虚拟条件句是指不能实现或纯假想的情况，可以对过去、现在或将来进行假想。我们可以记住这样一个原则，即把时态向过去推一格。接下来由小编为大家整理出if引导的虚拟条件句的用法，仅供参考，希望能够帮助到大家！
一、分清是虚拟语气还是真实语气
所谓虚拟语气，表示动作或状态，不是客观存在的事实，而是说话人的主观愿望、假设或推测。
遇到if引导的条件状语从句，首先，你应分清是真实条件句还是虚拟条件句。如果假设的情况是有可能发生的，就是真实条件句；如果假设的情况是过去或现在都不存在的，或将来也不大可能发生的，则是虚拟条件句。如：
it is fine tomorrow , I’ll go outing .（真实条件句）
you had come here yesterday , you would have seen him.（虚拟条件句）
二、分清虚拟的具体时间
对于if引导的虚拟条件句，结构比较复杂，主、从句，都得用虚拟，所以针对不同的句子，首先，你应根据主、从句判断是对何种时间的虚拟，即：现在、过去、还是将来，然后针对不同的时间，主、从句的谓语动词，用与之相对应的形式。为了掌握不同时间的虚拟，请大家掌握下面的表格。
动词形式
时间 从句 主句
与现在事实相反 动词过去式（be的过去式一般用were） Would
Should +动词原形
Could
might
与过去事实相反 Had+过去分词 Would
Should +have+过去分词
Could
might
与将来事实可能相反 动词过去式/should+动词原形 Were to +动词原形 Would
Should
Could +动词原形
might
e.g.1. 现在：If I were you,I should tell him the news.
2.过去：If I had had the money last week, I should have bought a car.
3.将来：If it were Sunday tomorrow,I should go to see my grandfather.
三、混合虚拟条件句
有时主从句时间不一致，针对这种情况主从句谓语动词应各按各的的情况，如：
you had listened to the doctor ,you would be all right now.（从句是对过去的.虚拟，主句是对现在的虚拟）
you had practiced speaking English more, you would be able to speak it fluently.(从句是对过去的虚拟，主句是对现在的虚拟)
四、省略if的虚拟条件句
在if引导的虚拟条件句中，如果从句中有were，had 或should,可以省略if,把这几个词放在主语之前，构成主谓倒装。(注意；省略连词if的倒装形式，其句首不能用助动词的缩略否定形式)
I you ,I Would not help him.
it not for you ,I would go to Beijing.（此句中not不前移。不能说Were not it for you ,I would go to Beijing.)
ld it rain ,the crops would be saved.
he been here , everything would have been all right.
总之，if引导的虚拟条件句是一个重点也是一个难点，需要多做练习才能加以巩固，熟练掌握。
