“It” 用法及其句型和固定搭配，是高中英语语法的重点、难点，又是近几年高考的热点，因此应给予充分的重视，现将it用法归纳如下：

一、It用作实词

表达以下概念：指代前文提到的事物，前文中的this，that；替代前文中的内容；指代一位性别不明的小孩或未知的人；指代未指明但谈话双方都知道的那件事；指代时间、天气、气候、距离等自然现象……

二、It用作形式主语

替代作主语的从句、动词不定式、动名词，而把真正作主语的从句、动词不定式、动名词置于句尾。

It 作形式主语的常见句型：

1. 代作主语的动词不定式，其句型为

（1）It be adj.（for sb.）to do sth.

此处adj. 通常为描述事件的形容词：easy，difficult，hard，necessary，unnecessary，possible，impossible，likely，unlikely，right，wrong，important，unimportant，legal，illegal，well-mannered，ill-mannered，polite，impolite，clear，obvious，certain，suitable，proper，fit，useful，useless，dangerous…

例  It is illegal（for a teenager）to drive a car without a license.

（2）It be adj. of sb. to do sth.

此处adj. 通常为描述人的形容词：kind，unkind，nice，rude，cruel，considerate，thoughtful，thoughtless，careful，careless，silly，foolish，stupid，clever，wise，crazy.

例  It's kind of you to help me with the problem.

（3）It替代作主语的动名词的常见句型

It's no good/use doing…

It's（well）worth doing…

It's（well）worth one's while doing/to do…

It's（well）worth while doing/ to do

例  It's no use crying over spilt milk.

2. It替代作主语的从句常见句型

（1）It is + noun +从句

例  It is no secret that the president wants to have a second term at office.

（2）It is adj. +clause

It's surprising that…（should）…  ……竟然……

It's a pity/shame that…（should）…  ……竟然……

例  It's important that you should apologize to her for your rudeness.（=It's of much importance that you should apologize to her for your rudeness.）

（3）It verb sb. + clause= It is v-ing + clause

It+surprise/delight/interest/disappoint/worry/disturb/annoy/amaze

/bother/concern/frighten/please/anger sb. that…

例  It worried me that she drove so fast.（= It was worrying that she drove so fast.）

（4）It verb（to sb.）that…= sb/sth verb to do

（verb = appear，seem，come about，emerge，follow，chance，happen，occur，transpire，turn out ，work out）

例  It（so）happened/chanced that they were out.（= They happened/chanced to be out.）

（5）It is v-ed that…=sb/sth is to do

（verb=say，report，think，believe，hope，expect，agree，accept，decide，determine，intend，plan，understand，know）

例  It is said that the couple have gotten divorced.（=The couple are said to have gotten divorced.）

（6）It is v-ed that …（should）…

（verb=demand，request，require，order，suggest，advise，recommend

例  It is suggested that they should begin with the third question.

三、It作主语的句型

1. It takes sb. … to do…（=sb takes…to do…）某人用多长时间做某事

例  It took the men a week to mend our roof.（= The men took a week to mend our roof.）

2. It's（just）（un）like sb. to do…（不）像某人做某事的风格

例  It was（just）like him to think of helping us.

3. It's（about/high）time that… should /v-ed…是该做某事的时候了

例  It's（about/high）time that we should take action.

4. It's the x-th time（that）… have v-ed…第几次做某事了

例  It's the third time that he has failed the driving test.

5. It is/has been… since …continuous v-ed（延续性动词）某动作已有多长时间不发生了

例  It's 10 years that he lived here

6. It was（not）… before…过（不）了多长时间某动作发生了

例  It was not long before they arrived.

四、It 作形式宾语

用来替代作宾语的从句、动词不定式、动名词，而把真正作宾语的从句、动词不定式、动名词置于句尾。

It 作形式宾语的常见句型：

1. verb+ it+ adj./noun（for/of）to do/clause （verb=think，believe，suppose，consider，feel，make，keep…）

例  I think it hard for you to do the task on your own./I think it hard that you'll do the task on your own.

2. verb+it+adj./noun（one's）doing（adj.=useless/worth/worthwhile）（noun=no use/no good/worth one's while/a waste of time/money/energy/words）（verb=think，believe，suppose，consider，feel，make，keep…）

例  I'll make it worth your while telling me about his secret.

3. verb+it+ important/unimportant/necessary/unnecessary/natural/essential that …（should）…

verb+it+of much/great/no/little importance that…（should）…

（verb=think，believe，suppose，consider，feel，make，keep…）

例  I think it important that you（should）attendthe conference.

4. verb + it+ as+ noun/adj.+ clause（verb=accept，regard，take，see，view）

例  The lecturer takes it as encouraging when so many students attend his lecture.

5. v. +it + prep. + that…

owe it to sb. that…把…归功于…

leave it to sb that…把…留给某人去做

take it for granted that …想当然

keep it in mind that…

例  Don't bother to arrange anything. Just leave it to me to sort out.

6. It用在不能直接跟宾语从句的动词后面，尤其是表示好恶的动词后，enjoy，like，love，dislike，resent，hate，don't mind，be fond of，feel like，see to  宾语从句紧跟it之后

例  I hate it  you can swim so well and I can't.

7. It用在不能直接跟宾语从句的介词后面，宾语从句紧跟it之后（except that例外）

例  I'm for it that you will follow their advice.

五、强调句型

It is/was+被强调部分+ that（who）… 强调句型用来强调谓语动词以外的任何句子成分。当被强调部分是人时也可以用who.

在使用强调句型时需注意以下几点：

1. 请注意强调句型的特殊疑问句

例  When was it that he changed his mind to take part in the activity？

2. 在强调原因状语从句时，只能强调由because所引导的从句

例  It was because he was ill that he didn't come to school yesterday.

3. 在强调not … until结构时必须把not与until一起放到被强调的位置上

例  It was not until she took off her dark glasses that I realized she was my brother.

4. 注意强调句型与定语从句的区别

例  It was at 7 o'clock that he came here yesterday.（ 强调句型）

It was 7 o'clock when he came here yesterday.（定语从句）

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