中高考考点——It形式主语句型大汇总（速藏）
形式主语，顾名思义，即形式上是主语，但实际上不是真正的主语，真正的主语是后面的动词不定式、动名词或主语从句等。如果让后面的动词不定式、动名词或主语从句用作主语，那么在句式上容易造成“头重脚轻”，句式不平衡，故往往用it作形式主语，而把真正的主语放在后面。it在这里没有任何意义。初中阶段，it作为形式主语常常用在以下几个句型。
、
It......+that +从句
一、It’s +形容词/名词+that +从句
（1）It is clear /obvious/true/possible/certain… that …
该句型中it 是形式主语，真正的主语是 that 引导的主语从句，常译为 “ 清楚（显然，真的，肯定……）”是主语从句最常见的一种结构。
It is very clear that he"s round and tall like a tree. = That he"s round and tall like a tree is very clear.
（2） It is important /necessary/ right/strange/natural... that ...+(should) do
该句型和上一个同属一个句型。由于主句中的形容词不同，that 后的从句中要用虚拟语气（should + 动词原形），should 可以省去。
It is necessary that you train yourself before the walk.It is important that you have your own support team.
二、It’s +名词+that +从句
（1）It is a pity ( a shame ... ) that ...
该句型中，that 后的从句一般用虚拟语气（should + 动词原形），should 可省去．表示出乎意料，常译为“竟然”。没有这种意义时，则不用虚拟语气。
It is a pity that such a thing ( should ) happen in your class.这种事竟然发生在你们班上，真是遗憾！ It is a pity that he is ill. 他生病了，真遗憾！
三、It happens (seems, looks, appears ) that...
该句型中it是形式主语，that 引导的是主语从句，主句中的happen, seem 等词是不及物动词．
It happened ( so happened ) that he met his teacher in the street. 碰巧…… It seemed that he didn’t tell the truth. 看来……
四、It’s +过去分词+that从句
惯用句型有：It is said that(据说), It is reported that(据报道), It is believed that(大家相信), It is hoped
that(大家希望), It is well known that(众所周知), It is thought that(大家认为), It is suggested that(据建议)等。
It is reported that 16 people were killed in the earthquake.
五、It is time ( about time , high time ) that ...
该句型中that 后的从句应该用虚拟语气，值得注意的是① 常用过去时态表示虚拟．② 有时也用should + 动词原形，should 不能省。常译为“是（正是）……的时候……”。
六、It is the first ( second … ) time that …
该句型要和上一个句型区别开来。该句型中的 that 从句不用虚拟语气，而用完成时态。至于用什么完成时态，由主句的谓语动词的时态决定。如果是一般现在时，后面从句用现在完成时态；如果是一般过去时，后面从句则用过去完成时态。该结构中 that 可以省去；it 有时用 this 替换，常译为“是第一（二）……次……”。
It is the first time I have been here.
= This is the first time I have been here.
It’s +......+to do sth
一、It’s +形容词+(for sb) +to do sth
（1）It is necessary ( for sb. ) to do sth.
该句型与上一个同属一个句型。如果不定式的逻辑主语是由for 引起，主句中的形容词通常是表示重要性，紧迫性，频繁程度，难易，安全等情况的形容词。常见的形容词有：
① important, necessary, natural
② easy, safe, common, normal, hard, difficult, dangerous, unusual, rare, impossible, pleasant 等。
在①中的形容词作表语可以用从句改写，如：
It is important for her to come to the party.
= It is important that she (should ) come to the party
It is difficult to walk through eight country parks.
It’s +形容词+(of sb) +to do sth
（2）It is kind ( of sb. ) to do sth.
该句型中的不定式短语是真正主语，如果不定式的逻辑主语是由 of 引起，主句中的形容词必须是能表示逻辑主语特征的形容词。常见的有: bad, brave, careless, clever, cruel, foolish, good (好心的), honest, horrible, kind, lazy, modest, naughty, nice (有教养的), polite, rude, silly, stupid, wise, wrong (错误的)等。 这个句型可以改写为：sb. is kind to do sth.
It is kind of you to say so. = You are kind to say so.
特别提醒：
☆该句型的否定结构为It’s +形容词+(for/of sb) +not+to do sth
It is very important not to give them too much food. (7B 100)
It is very polite not to speak loudly in public.
☆该句型有时可以与It is + adj. + that从句的句型互换使用，意思不变。如：
It is necessary for you to train yourself before the walk.
= It is necessary that you will train yourself before the walk.
（3）注意：It is no good (use ) doing sth.
该句型中的真正主语是动名词短语，主句中的表语可以是no good , ( not any good ) , no use , ( not any use )。
二、It’s +名词+to do sth
It’s everyone’s duty to obey the law.
It is my turn to clean the blackboard.
三、It takes sb +some time to do sth
该句型中的不定式是真正的主语，it是形式主语，句型中的直接宾语是时间。常译为“做……要花费某人……”
It took us two hours to set up the stage.
特殊句式
一、强调句
（1）It is/was + 被强调部分 + that/who ...
该句型是强调句型。被强调部分可以是主语，宾语，表语或状语。强调的主语如果是人，that 可以由 who 换用。如果把这种句型结构划掉后，应该是一个完整无缺的句子。这也是判断强调句型与其它从句的方法。
（2）It is not until + 被强调部分 + that ...
该句型也是强调句型。主要用于强凋时间状语，译成汉语 “直到……才……”，可以说是 not ... until ... 的强调形式。
It was not until she took off her dark glasses that I realized she was a famous film star.= Not until she took off her dark glasses did I realize she was a famous film star.= I didn"t realize she was a famous film star until she took off her dark glasses.
二、It形式主语的状语从句
It is… since ...
该句型主要用作处理瞬间动词的完成时，又要和表示一段时间的时间状语连用的问题。主句中是时间作表语，其时态是现在时或完成时，since 引导的从句通常是一般过去时态，而且是瞬间动词。如果主句是一般过去时，从句则用过去完成时。
It is ... when ...
该句型中的 when 引导的是一个时间状语从句，主句中的 it 指时间，表语由具体的时间充当。常译为“当……的时候，是……”。
It be ... before ...
该句型主句中的 it 指时间, 主句中的时态常是将来一般时或过去时两种时态．主句中的表语多是long, not long , 3 days , 2 weeks 等表示时间段的词或短语。常译为“……之后……”。
It doesn"t matter whether ( if ) ...
该句型中whether (if) 引导的从句是真正主语，该句型常译为“不论（是否）…… 没关系……。
It looks ( seems ) as if ...
该句型中it 无意义。 as if 引导一个状语从句。常译为，“看起来好象…… ＂如果与事实不相符合，则用虚拟语气