l. 时间选择型
当虚拟语气用来表示一种不能成为现实、不真实的情况时，须选择与现在、将来和过去情况相反的三种不同时间，从而决定谓语动词。这类虚拟语气主要用于如下几方面:
（1）虚拟条件句（含蓄虚拟条件句）
If l were you，l would study much harder．（与现在情况相反）
If he did（were to do，should do）it，he would do it well．（与将来情况相反） I wouldn't have finished the work without your help．（与过去情况相反）
（2）由 even if（though）引导的让步状语从句，其谓语动词变化同于虚拟条件句，在口语中也可用直陈语气。
Even if he were here, he wouldn't be able to help you．（与现在情况相反）
Nothing could have saved your father，even if the doctor had arrived on time．（与过去情况相反）
（3） wish后的宾语从句
I wish I were five years younger than you．（与现在情况相反）
He wishes you would go with him.（与将来情况相反）
I wished I had won the match．（与过去情况相反）
注意：wish的时态不影响从句三种时间的判定。
（4） as if（though）引导的表语从句和方式状语从句
He looks as if he were very sleepy．（与现在情况相反）
They are talking about something，as if they were quarrelling with each other．（与现在正发生的惰况相反）
2．should+动词原形型
这种类型的虚拟语气一般用于主语从句、宾语从句、表语和同位语从句。谓语由should+动词原形构成，无论什么人称都不能用 would，should在口语中可以略去。
（1）在主语从句中用以表示惊奇、惋惜、理应如此，构成 It is natural（important, necessary，strange，a pity，a shame等）that… 句型。
It is natural that you should say apology to him．
It is a pity that you should be careless．
（2）用于表示命令、建议一类动词后的宾语从句，如：suggest，move，insist，demand，request，command等。
The young man insisted that he should be sent to do the work．
I suggested that we should set off earlier．
应注意：当insist表示对已发生过的事物的看法，或当suggest为“说明了”，“暗示”的含义时，从句用直陈语气而不用虚拟语气。
The Arab insisted that he hadn't seen the camel．
His smile suggested that he was happy．
（3）当表示间接的要求、建议、命令、决定等名词作主语时，其表语从句用 should+动词原形。这类名词有 suggestion，request，order，advice，idea等。
The officer's order was that his soldiers should repair the defence works at once． His advice is that your father should do more exercises in the morning．
（4）上述名词的同位语从句也应用should+动词原形。
I did not receive the order that you should leave here at once．
His suggest on that you should keep silent is reasonable．
3．一般过去式型
这类虚拟语气的谓语动词一般用动词过去式表示，常用于如下几个方面：
（1）用would，could，might表示说话人的谦逊、客气、婉转。
Could you tell me the way to the cinema？
Would you mind my smoking here？
（2）用于so that和 in order that引导的目的状语从句。
They are climbing higher so that they could see the whole city．
但从句若要否定的话则用shouldn’t。
He locked the door of his room in order that he shouldn't be troubled by someone．
（3）用于It is time that 句型。
It is time that the problem was solved．
在此句型中也可用should+动词原形。应注意该句型若用过去式表示时，第一、三人称单数不可用were代替was。
4．动词原形型
该类型虚拟语气谓语仅用动词原形，第三人称单数也不加“s”
（1）表示强烈愿望。
God save me．
Heaven help us．
（2）用may放在句首表示说话人对对方的祝愿和祝福。
May you be happy．
May you secceed.
第二篇：虚拟语气总结
英语中的语气分为陈述语气、祈使语气、虚拟语气三类。
虚拟语气用来表示说话人的主观愿望或假想，而不表示客观存在的事实，所说的是一个条件，不一定是事实，或与事实相反。当一个人说话时欲强调其所说的话是基于自己的主观想法，愿望，假想，猜测，怀疑或建议，而不是根据客观实际，就用虚拟语气。
虚拟语气通过谓语动词的特殊形式来表示。
If I were you, I would go at once.如果我是你，我马上就会去。
If there were no air, people would die.如果没有空气，人就会死亡。 用法及动词形式
1、表示与现在事实相反的情况：
从句：主语+过去时 主句：主语+should/would/could/might+do 1.If I were you, I would take an umbrella. 如果我是你，我会带把伞。 2.If I knew his telephone number, I would tell you. 如果我知道他的电话号码，我就会告诉你。
3.If there were no air or water, there would be no living things on the earth.如果没有水和空气，地球上就不会有生物。
2、表示与过去事实相反的情况
从句：主语+had done 主句：主语+should/would/could/might+have done
1. If I had got there earlier, I should/could have met her.
2.If he had taken my advice, he would not have made such a mistake.
3、表示对将来情况的主观推测
从句：①if+主语+were to do 主句：①主语+should/would/could/might+do ②if+主语+did/were ②主语+should/would/could/might+do
③if+主语+should+do ③主语+should/would/could/might+do
1.If he should come here tomorrow, I would talk to him.
2.If there were a heavy snow next Sunday, we would not go skating.
当虚拟条件句的谓语动词含有were, should, had时，if可以省略，这时条件从句要用倒装语序，即把were, should, had等词置于句首。 Should he agree to go there, we would send him there.
Were she here, she would agree with us.
6、非真实条件句中的条件从句有时不表达出来，只暗含在副词、介词短语、上下文或其他方式表示出来，这种句子叫做含蓄条件句，在多数情况下，条件会暗含在短语中，如without…, but for…等
But for his help, we would be working now.
Without your instruction, I would not have made such great progress.
8.注意，在虚拟语气的从句中，动词be的过去时态一律用were，不用was。
各类用法
1、wish 后宾语从句
a、表示与现在事实相反的愿望，谓语动词用过去式
eg. I wish I had your brains.
b、表示与过去事实相反的愿望，谓语动词：had+done
eg:.I wish I had known the truth of the matter.
c、表示将来难以实现的愿望 谓语动词：should/would（情态动词） + 动词原形
eg. I wish I should have a chance again.
(注：if only引导的感叹句和as if/as though引导的状语从句也有相同用法）
2、在so that, in order that所引导的目的状语从句中，从句中的谓语为：can / could / may / might / will / would / should + do。
He goes closer to the speaker so that he can hear him clearer.
He read the letter carefully in order that he should not miss a word.
3、一想要(desire一宁愿(prefer)二命令(order. command)三建议(advise. suggest. propose)四要求(demand. require. request. ask.insist)中，无论主句谓语动词为何种时态，从句的谓语动词都用："should + do"。should可以省略。eg：
He suggested/ insisted/ demand /ordered that we (should) takethe teacher's advice.
4、insist意为“坚持某种动作”才用虚拟语气；意为“坚持某种观点，某个事实”则不用虚拟语气。
He insists he is a student. 他坚持说他是个学生。
这个语句表示的是事实，因此在这个语句中不能使用虚拟语气。
suggest意为“建议”才用虚拟语气，意为“暗示”则不用虚拟语气。
His face suggests that he looks worried .本身是事实，因此它就没有用到虚拟语气。
5、表情绪.观点的形容词或名词也要用虚拟语气.如:necessary、important、impossible、natural、strange、surprising、funny、right、wrong、better、a pity等。
句型：It is.......that +主语从句，从句的谓语动词都要用should+原型 或只用动词原型。
It is srange that such a person should be our friend.
6、 在even if, even though 所引导的让步状语从句中，可用虚拟语气，主句、从句的结构与if所引导的条件从句结构相同。
Even if he were here himself, he should not know what to do.
即使他亲自来也不知该怎么办。（事实：他没来）
Nobody could save him even though Hua Tuo should come here.
即使华佗在世也救不了他。（事实：华佗不在世）
7、 在whatever，whichever，whenever，whoever, wherever，however, no matter wh-等引导的让步状语从句中，从句虚拟语气结构为：
指现在或将来： may +do。
We will finish it on time no matter what may happen.
不管发生什么事，我们都要按时完成。
I will wait for him no matter how late he may come.
不管他来的多么晚，我都会等他。
指过去： may +have done 。
You mustn't be proud whatever great progress you may have made.
不管你取得了多么大的进步，你也不能骄傲。
We must respect him no matter what mistakes he may have made.
不管他犯过什么错误，我们必须尊敬他。
8、一般would rather, had rather, would sooner等之后的宾语从句常表示与客观事实不相符的一种愿望，故使用虚拟语气。其虚拟语气的结构为：
过去 had + done
现在 过去时(be 用were )
将来 过去时(be 用were )
I'd rather you had seen the film yesterday. 我倒想你昨天看过了这场电影。 I'd rather you were here now. 我倒想你现在在这儿。
We'd rather you went here tomorrow. 我们倒想你明天去那儿