下面是小编帮大家整理的英语四级情态动词讲解（共含7篇），希望对大家有所帮助。同时，但愿您也能像本文投稿人“lt883721”一样，积极向本站投稿分享好文章。
情态动词有一定的意义，表示人的看法和态度，不表示动作或状态，因而不能单独做谓语，必须和实意动词或系动词的原形一起构成谓语，没有人称和数的变化。把情态动词放在句首、句尾用问号便构成疑问句;在其后加上not或never等否定词就构成否定句。如：
My mother can drive. 我妈会开车。
My mother can’t drive. 我妈不会开车。
Can your mother drive? 你妈会开车吗?
Can’t your mother drive? 你妈不会开车吗?
You needn’t look at me like that. 你不必那样瞧着我。
常用的情态动词有can, could; may, might; must; should; need; dare; ought to 等。
(一)can/could 的用法
1、表示具备某种“能力”，但不一定做事情。仅仅表示有能力而已。can表示现在;could表示过去。如：
The nine-year old boy can swim across the river. 那个九岁的男孩能游过那条河。
Can you swim across the river? 你能游过那条河吗?
I could do such things then, but I can’t now. 我那时候能做这样的事情，但现在不能了。
We couldn’t get the truck to start. 我们发动不了那辆卡车。
2、表示“请求”(疑问句中)、“允许”。Could 比 Can 委婉;两者都指现在。回答一律用 can 或 cannot, 也可以用mustn’t. 如：
Can /could I smoke here? 我可以在这里抽烟吗?
Yes, you can. 是的，你可以。
No, you cannot smoke here. 你不能在这里抽烟。
You can go now. 你现在可以走了。
Could you lend me $55? 你能借给我55美圆吗?
Yes, of course. 当然可以。
No, I cannot/I’m sorry I cannot. 不，不行/对不起，恐怕不行。
Could you tell me where John is? 你能告诉我约翰在哪儿吗?
3、表示“可能性”。 但是并不牵涉到是否真会发生：都可以表示现在和将来，只是could的语气更加不肯定。如：
That can/could be very awkward. 那可就太尴尬了。
Can/Could it be true? 那会/可能是真的。
That can’t/couldn’t be true. 那不可能是真的。
Will you answer the phone? It could be your mother. 你去接电话好吗?可能是你妈妈。
What can/could they be doing? 他们可能会在干吗呢?
Could/Can they be chatting in his office? 他们可能在他办公室里聊天吗?
No, they can’t/couldn’t be doing that now. 不， 现在他们不可能在做那事。
(二)may/might 的用法
1、表示允许或请求允许;might语气更礼貌：
May I turn on the TV? 我可以把电视打开吗?
You may go home now. 你现在可以回家了。
She asked if she might have my bike. 她问是否可以借用我的自行车。
He told me I might go and see him any time. 他和我说我可在任何时候去见他。
can/could和may/might 都可以表示允许和请求允许。can最直截了当;could 礼貌客气;may 既尊重又婉转礼貌;might 带者太多的虚礼，所以很少使用。如：
对所有这些问句的肯定回答：
Yes, of course. Yes, you can/may.
对所有这些问句的否定回答：
No, you can’t/may not /mustn’t /I’m afraid not.
2、表示可能性，是“也许”之意。这时may和might无时间上的差别，只是might在语气上更不肯定一些。如：
You may/might have some fever. 你也许发烧了。He said that the news might be true. 他说这消息可能是真的。
They may/might be having a bath. 他们也许正在洗澡。
We may be buying a new house. 我们也许要买个新房子。
表示可能性时，may/might不用于疑问句，可用can/could或别的说法。如：
Is it likely to rain, do you think? 会下雨吗，你认为?(不说May it rain?)
Can/could they be having a bath? 他们可能正在洗澡吗?
(三)must的用法
1、表示义务、命令或劝告，是“必须”之意。对自己、对别人均可：
We must take this seriously. 我们必须严肃对待这事。
You must tell me the truth. 你必须和我说实话。
Patients must use medicine according to the doctor’s orders. 病人用药必须遵医嘱。
在回答由must引起的问题时，如果是否定回答，多用needn’t 或 don’t have to，表示“不必、没必要”;而mustn’t表示“绝对不行、不可以”的意思，有时用来回答can或may开头的问句，表示口气很强的不允许：
Must the ladies wear dresses? No, they don’t have to/they needn’t. 女士们必须着连衣裙吗?不，不必。
Can/May I come in? No, you can’t/mustn’t. 可以进来吗?不行/绝对不行。
must 仅用于表示现在和未来。其他时态用have to。但在间接引语中可用must表示过去:
I had to leave early because I wasn’t feeling well. 我不得不早点离开，因为我觉得不舒服。
You’ll have to take care of the child. 你将不得不照顾这个孩子。
She has had to work over ten hours a day. 她一直不得不每天工作十几个小时。
They decided they must stop smoking. 他们决定他们必须戒烟。
He asked me if he must leave at once and I told him he didn’t have to. 他问我是否他必须马上离开，我告诉他不必。
2、表示推测，是“肯定、一定”之意。此时，must只用于肯定句。在否定句或疑问句中，用can/could：
There must be a mistake. 准是弄错了。
Can/Could there be a mistake 可能会有错吗?
There can’t/couldn’t be a mistake. 不可能会有错吗?
He must be over sixty now. 他肯定六十多岁了。
He can’t/couldn’t be sixty now. 他现在不会是六十岁。
Can/Could he be over sixty now? 他现在会有六十多岁吗?
They must be watching the news now. 他们这会儿肯定在看新闻。
They can’t/couldn’t be watching the news now. 他们这会儿不可能在看新闻。
Can/Could they be watching the news now? 他们这会儿可能在看新闻吗?
我们先对表示“推测”的表达法作一个总结：
(1)表示对现在和将来状况的推测：must 一定，may 可能，might 也许，can’t 不可能。从“一定”到“不可能”，可能性逐渐降低。
(2)对已经过去的情况的推测：must, may, might, can’t/couldn’t 这些词后面分别加上have + 过去分词，表示“一定…”，“可能…”， “也许…”，“不可能…”。从“一定”到“不可能”，可能性逐渐降低。
一、Should 表示过去将来时，即从过去观点看将来要发生的是，多用于间接引语中。
We thought that we should never see you again. 我们想我们再也看不到你了。
The BBC weather report this morning said that we should have rain.今天早上，BBC电台天气报告说，今天有雨。
二、Should 表示义务、责任、常译为“应当”，“应该”，或表示一种估计的情况，译成“按理应当”，“估计......”。
Why should I pay him? 为什么我该付给他钱?
They should be there by now， I think. 我估计，他们现在到那儿了。
Should 用于完成时态，表示对过去发生的动作的一种推测，译成“应该已经......”。
You should have washed the wood. (But you haven't.) 你应该把伤口清洗了。(然而你没有)
三、Should 用于虚拟语气中。
(1)用于It is necessary (important， strange.。。that.。。)中，在美国英语中should 常省去。
It is important that we (should) learn English well. 我们学好英语很重要。
(2)用于It is ordered (suggested)that.。。中，而在美语中should常省去。
It is decided that we (should) finish our work in a week.决定我们要在一周之内完成我们的工作。
(3)用于表示命令、请求、建议、决定等词后面的宾语从句中，在美国英语中should常省去。
He wrote， suggesting that Mr. Wang (should) come to Beijing. 他信中建议王先生到北京来。
The commander ordered that the city (should) be taken in five days.司令员下令必须在五天之内占领这座城市。
(4)should用于表示命令、请求、建议、决定等词后面的表语从句，同位语从句中，在美国英语中should 常省去。
We all agreed to his suggestion that we (should) go to Beijing for sightseeing.我们都同意他的意见，去北京观光。
My idea is that we (should) do exercises first. 我的意见是我们先做练习题。
(5)用于if引导的从句中，表示与将来事实可能相反的假设。
If it should rain tomorrow， we would stay home. 如果明天下雨，我们就呆在家里。
四、在条件状语从句中，should 表示“万一”，即可表示不能实现的假设，又可表示可以实现的假设。
If he should fail to come， ask Comrade Cheng to work in his place.万一他不来，就叫陈同志代替他的工作。
Should it rain tomorrow， the meeting would be put off. 万一明天下雨，会议就延期。
五、在某些从句中，should 表示惊异、意外等情绪，常译为“竟然”。
It seems unfair that this should happen to me.真不公平，这件事竟然发生在我身上。
六、should 用于主句中，主语是第一人称，表示某一条件下所产生的必然结果，并与事实相反;当主语是第二、三人称时，表示说话人或执笔人的意志或看法。
If I met her， I should tell her about it. 如果我碰到他，我肯定会将此事告诉他。
If he had much money， he should buy it. 如果他有很多钱的话，我就让他买了。
七、当陈述部分含有ought to ，其反意疑问句部分，美国英语中用should . She ought to stay here， shouldn't her?她该留在这儿，是吗?
八、用于成语中 I should like to......“我想(做)......”
I should like to ask the teacher a question. = I should love to ask the teacher a question. 我想问老师一个问题。
1. 三者都可表示“除外”，但 besides 表示一种累加关系，意指“除了什么之外，还有……”;而 except 或 but 则表示一种排除关系，意指“除了什么之外，不再有……”。如：
Besides his wife，his daughter also went to see him. 除他妻子外，他女儿也去看过他(即妻子女儿都去看过他)。
Nobody went to see him except [but] his wife. 除他妻子外，没有一个人看过他(即只有他妻子去看过他)。
注：在否定句中，besides 也表示“除……之外不再有…… ”，与but, except 同义。如：
No one passed the exam besides [except] Jim. 除吉姆外，没一个人通过考试。
2. 关于 but 与 except：
(1) 两者都可表示“除……外不再有……”，但含义上略有差别：but侧重指意义的几乎完整性，而 except 则侧重指后面除去的部分。比较：
All are here but one. 除一个人都到了。
All are here except one. 还有一个人没到。
(2) 在现代英语中，but 的介词用法十分有限，一般说来，它只能用在下列词语之后：
① no, no one, nobody, nothing, nowhere 等
② any, anyone, anybody, anything, anywhere 等
③ every, everyone, everybody, everything, everywhere 等
④ all, none 等
⑤ who, what, where 等
Everyone knows it but you. 除你之外大家都知道。
I haven't told anybody but you. 除你之外，我没告诉任何人。
No one but he [him] showed much interest in it. 除他之外没有一个人对此有很大兴趣。
一般说来，若没有出现上述词汇，就不宜使用介词 but，否则可能造成错句。但是 except 却没有以上限制。比较：
正：The window is never opened except in summer. 除夏天外，这扇窗户从不打开。
误：The window is never opened but in summer.
(3) but 一定不能用于句首，except 通常不用于句首：
除我之外每个人都累了。
正：Everyone is tired but (except) me.
正：Everyone but (except) me is tired.
误：But (Except) me, everyone is tired.
注：except for 可用于句首，表示 except 的意思：
正：Except for me, everyone is tired.
3. 关于 except 与 except for：
except 主要用来谈论同类的东西，而 except for 则主要用来谈论不同类的东西，有时含有惋惜之意。如：
All compositions are well written except yours. 除了你的作文外，其他的作文都写得很好。
His composition is good except for a few spelling mistakes. 他的作文写得不错，只是有几处拼写错误。
注：若用于句首，则 except for 与 except 同义(但 except 通常不用于句首)。
4. 关于 except for 与 but for：
except for 主要表示排除，but for 主要表示一种虚拟条件(与虚拟语气连用)。如：
Except for me, everyone passed the exam. 除了我之外，大家都通过了考试。
But for my help, she would not have passed the exam. 若不是我的帮助，她就不会通过考试。
But for the atmosphere plants would die. 如果没有大气，植物就会死亡。
5. besides 除用作介词外，还用作副词，其意为“此外”、“而且”，可用于分句句首(通常用逗号隔开)或句尾。如：
I don't want to go; besides, I'm too tired. 我不想去，而且我也太累了。
This car belongs to Smith, and he has two others besides. 这部车是史密斯的，此外他还有两部。
高二英语情态动词语法讲解
情态动词顾名思义就是表示情感和态度的词，常见的有：can (could); may (might); must; have to; shall (should); will (would); need; dare (dared); ought to; 情态动词没有人称和数的变化，不能单独使用，它与其后的动词原形合成谓语结构。它们的用法如下：
一. can和could 的用法
1. 表示能力或客观的可能性，还可以表示请求和允许。如：
Can you finish this work tonight? Man cannot live without air.
Can I go now? Yes, you can.
注意：
1) could表示语气较委婉的请求，主要用语疑问句，(用于此意义时不用在肯定句)答语用can。
Could I come to see you tomorrow?
Yes, you can. (不能用could). (否定句常用No, Im afraid not.)
2) can表示能力时，还可以用 be able to 代替，例如：
Ill be able to come this afternoon.
但当我们要表示某件事已成时，须用 was (were) able to不能用could，例如：
He was able to go to the party yesterday evening and he enjoyed himself very much.
2. 表示惊异、怀疑、不相信的态度。(主要用在否定句、疑问句和感叹句中)
Can this be true? How can you say like that? This cannot be done by him.
3. can (could) + have + done 的疑问或否定形式表示对过去发生的行为怀疑或不肯定。
He cannot have been to that town. Can he have got the book?
二. may 和might 的用法
1. 表示许可，表示请求、允许时，might 比may 的语气更加委婉一些，否定回答时可用cant 或mustnt, 表示不可以、禁止、阻止之意。 例如：
Might I use your pen? No, you mustnt.
May I take this book out? Yes, you can ( No, you cant/ mustnt.)
用May I 征询对方许可在文体上较正式，在口气上比较客气，在日常口语中，用Can I 征询对方意见在现代口语中更为常见。
2. 用于表示祝愿的句子中。例如：
May you success! May you be happy! May you have a good journey!
3. 表示推测、可能(疑问句中不用于此意)
He may be very busy now. (此句中用might 语气较弱)
4. May (Might) + have + done 表示对过去发生的行为的推测。例如：
He may not have finished the work. (此句中用might 语气较更弱)
三. must 和 have to 的用法
1. 表示必须、必要。
You must come on time.
当must 引出的问句时， 若是否定的回答，不能用mustnt，而用neednt或dont have to.
Must we hand in our exercise our books today?
Yes, you must. (No, neednt/you dont have to.)
2. must be + 表语的结构表示推测，它的否定或疑问形式用can 代替must。如：
He must be our new teacher.
Can he be our new teacher? He cant be our new teacher.
※ 附加疑问句要和谓语动词实际时态一致。如：
He must be our new teacher, isnt he?
3. must + have +done 的结构常用在肯定句中，表示对过去或完成的情况推测，它的否定或疑问形式也用can代替must.
He must have finished his work.
※ 附加疑问句也要和谓语动词实际时态一致。如：
He must have finished his work already, hasnt he?
He must have finished his work at four yesterday, didnt he?
4. have to 的含义与must相似，两者往往可以互换使用，但have to有各种形式，随have的变化而定，must 与have to有下列几点不同：
1) must表示的是说话人的主观看法，而have to则往往强调客观需要，例如：
The play is not interesting. I really must go now.
I had to work when I was your age.
2) 两者的否定意义大不相同。例如：
You mustnt go. (你不可以去) You dont have to go. (你不必去)
3) 询问对方的意见时应用must。
Must I hand in the exercise book before eight?
4) must 表示偏偏
Must it rain today? (今天怎么偏偏下雨呢?)
四. dare 和need的用法
1. need表示需要，必须，作情态动词时，仅用于疑问句和否定句，在肯定句中一般用must, have to, ought to,或should代替。例如：
You neednt come so early.
Need I clean all the room right now? Yes, you must. ( No, you neednt.)
注意：neednt + have +done表示本来不必要做的'事而实际上做了，例如：
You neednt have waited for me. 你本来没有必要等我的。
2. dare作情态动词时，主要用于疑问句，否定句和条件句中，一般不用于肯定句，例如：
How dare you take my book without permission?
He dare not speak English before such a crowd, dare he?
3. need和dare作情态动词时，过去时形式与现在形式相同(美国英语中可用dared)。
He was so angry that no one dared say a word.
They said that he neednt stay there any longer.
4. need和dare常用实义动词，有时态、人称和数的变化。不同的是dare作实义动词时，在肯定句中通常接带to的不定式，在疑问句和否定句中，dare之后的不定式可带to或不带to。例如：
He needs to finish the work before nightfall.
I dare to swim across this river.
He does not dare (to) answer the teachers question.
Dont you dare (to) touch it?
I wonder he dared say that.
5. I dare say是习惯用语，常可写为I daresay，用法有以下几种：
1) 敢于说，通常接that或what引导的名词性从句。
I dare say that he has stolen Toms football. I dare say what I think.
2) 我想;恐怕;大概;也许是，通常作插入语用，使句子委婉。
I dare say there is something wrong with the machines.
Youre tired, I dare say.
You, I dare say, think otherwise.
3) I dare say往往也作为反语使用。
Oh, you mean to defeat our football team? I dare say you will. (噢!你们想赢我们的足球队?也许可以吧。)
五. shall和should的用法。
1. shall用于第一人称疑问句。表示征求对方意见。
What shall we do this evening?
Shall I open the window?
2. shall 用语第三人称疑问句中，表示说话人征求对方的意见或向对方请示。
When shall he be able to leave the hospital?
3. shall用于第二、三人称的陈述句，表示说话人给对方的命令、警告、允诺或威胁。
You shall fail if you dont work harder.
He shall have the book when I finish reading.
He shall be punished.
4. should表示劝告、建议、命令，其同义词是ought to，在疑问句中，通常用should代替ought to.
You should go to class right away.
Should I open the window?
5. should + have +done应该做的事实上没做;shouldnt have done不该做的事却已经做了，常含有责备的意思。
You should have started earlier this morning.
You shouldnt have treated her like that.
六. will和would的用法。
1. 用于疑问句表示请求、建议等，would比will的语气更加委婉。
Will you please give me a hand?
Would you mind my smoking here?
2. 表示意志、愿望和决心。
I will never do that again.
They asked us if we would do that again.
3. 用will be和will have done的结构表示推测，主要用于二、三人称，前者表示对目前的情况的推测，后者表示对已经完成的动作或事态的推测。
This will be the book you want.
He will have arrived by now.
4. would可表示过去反复发生的动作或某种倾向，表示过去习惯时比used to正式，同时它没有现在已无此习惯的含义。
I would visit him during my vacation.
The patient would not recover.
5. 表示料想或猜想。
He would be your new teacher.
He would not come any more.
七. ought to的用法。
1. ought to表示应该时意义与should基本一致，但更侧重于一种义务或责任。
You ought to take care of him.
Parents ought to bring up their children.
2. 表示推测，注意与must表示推测时的区别。
He must be home by now.
He ought to be home by now.
This is where she must be.
This is where she ought to be.
3. ought to have done的用法与should have done的用法相同
注意：ought to在美国英语中，用于否定句和疑问句时，to可以省略。如：
Ought you smoke so much?
You oughtnt smoke so much.
八. used to; had better; would rather的用法。
1. used to表示过去习惯动作或状态，现在已经不存在，在间接引语中，其形式可不变。如：He told us he used to play football when he was young.
1) 在疑问句、否定句或否定疑问句中，可有两种形式。
疑问句：Did you used to/Used you to go to the same school as your brother?
否定句：I usednt to/didnt use to go there. (usednt 也可为usent, 发音不变)。
否定句疑问句：Usednt you to/Didnt you used to be interested in the play?
2) 在附加疑问句和简略答语中，也可有两种形式。
She used to be very fat, didnt/usednt she?
Did you used to/Used you to play chess? Yes, I did/used to.
2. had better意为最好，后接不带to不定式。
We had better go now.
Hadnt we better stop now?
I think Id better be going.
You had better have done that.
3. would rather意为宁愿，表示选择，后接不带to的不定式。
Id rather not say anything.
Would you rather work on a farm?
Wouldnt you rather stay here? No, I would not. Id rather go there.
由于would rather表选择，故后面可接than.
I would rather watch TV than go to see than go to see the film.
I would rather throw it away than you should get it.(若than后面接从句常用should do)
Id rather you didnt talk about this to anyone.
※ would rather 还可写为would sooner/would as soon.
1.助动词：辅助其他动词构成时态、语态、疑问句式、否定名式的动词。助动词有些词义，有些没有词义，或者暗含一点词义。放在谓语首位置助动词会受主语人称、数的限制，其他位置不会受限制。
2.英语中有19个助动词：
do does did
shall will should would
have has had having
be am is are was were been being
3.情态动词：放在谓语动词的首位，辅助其他动词构成谓语，给谓语增加“可以，愿意，能够，应该，必须”等意思。
情态动词的性质、作用与助动词相同，除了给谓语增加一点意思外，还代替助动词与其他动词构成疑问句式和否定句式。但它们没有人称、数的变化，并且只能用在谓语中，不能用于为以外的成分中。
4.英语的情诚动词有：
5.助动词和情态动词的对比：
can’t, couldn’t表示否定的推测:
She can’t be serious.
A more suitable book can’t be found. (It is not possible to find a more suitable book.)
He couldn’t (can’t) be over fifty.
情态动词后接进行式, 完成式和完成进行式:
a) 情态动词可以和动词的进行式构成谓语, 表示”应该正在…”, “想必正在…”这类意思:
Why should we be sitting here doing nothing?
This isn’t what I ought to be doing.
She might still be thinking about the question you raised.
They must (may) be waiting for us, let’s hurry up.
They can’t be using the room now.
b) 情态动词有时和动词的完成形式构成谓语, 表示”应当已经…”, “想必已经…”这类意思:
I should have thought of that.
They shouldn’t have left so soon.
She must have arrived by now.
You needn’t have told them that.
Where can (could) he have gone?
He can’t have finished the work so soon.
He may not have achieved all his aims. But his effort is praise-
worthy.
We ought to have give you more help.
c) 情态动词间或也可以和一个动词的完成进行式构成谓语,表示”应当一直在…”, “想必一直在…”这类意思:
They are sweating all over. They must have been working in the fields.
They may have been discussing the problem this morning.
You should have been waiting for us. Why haven’t you?
She couldn’t have been swimming all day.
