高考重点：It的用法以及含有it的句型英语中it 一词结构看似简单，但其词义广泛，使用范围很广，常令一些初学者感到头痛。
It用法及其句型和固定搭配，是英语语法的重点、难点，又是近几年考试的热点,在高考中也是重现率较高的语言点，其考查方式多通过“单项填空”进行，偶尔也出现在“短文改错”和“完形填空”中。
因此在复习中应给予足够的重视。
下面笔者就it的用法简单归纳如下。
一、代替上文中提到过的人或事物。
指代人时，一般用于小孩或身份不十分明朗的人。
1) －Who is the baby? －It‘s my teacher’s son．2) －Who is that gentleman? －It's my friend Tom．He(不可用It) wants to see you．不定代词one 指代前文提到的同类事物之一，而it 特指上文中提到的同一事物。
试对比：This pair of shoes is small. May I have another one？（泛指的另一双）这又鞋子太小了，再拿一双给我看看好吗My pen is missing.Ican’td find it.我的钢笔丢了找不到了(it指my pen)二. it 作为无人称动词的主语，表示天气，时间，距离，环境情况等等。
这时的it 不指某个具体的东西。
没有明确的含义。
译成汉语可不必译出来。
如1).It‘s half an hour’s walk from here to our school．从这儿到我们学校是步行一个小时的路程2) It‘s nice and warm here．这里非常暖和3) But it's two o'clock now, and it's time for us to go to school．两点了该是上学的时间了4) It’s quite close in the room . Let’s open the window for a while。
房间里太闷，把窗子打开一会儿吧。
三.“It”可以代替指示代记词This ,that .例：---Whose dictionary is that ?---It is mine四,用作形式主语或形式宾语。
1. 当作主语的不定式、－ing短语或从句太长时，往往用it作形式主语，而将真正的主语移至句末，以避免句子头重脚轻。
it作形式主语的常见句型：★it替代动词不定式作主语的常见句型为:1) It is necessary /important /possible/easy…..for sb to do….如:It is necessany to learn a foreign lanuage.学一门外语是有必要的。
It is kind /foolish/polite/brave/careless…of sb to do.常用形容词有:clever/wise/bright/silly/foolish/stupid/kind/cruel/right/wrong等如:It is kind of you to help me=Y ou are kind to help me.:谢谢你帮助我.3)It is up to sb to do sth.该由某人做某事如:It is up to you to decide.由你来决定.4)It is (not)like sb to do sth.做某事是(不)是某人的行为.如:It was not like you to have said such rude words. 说出这样粗鲁的话不像你的行为.5)It is one’s turn to do sth.轮到某人做某事.如;It is your turn to speak 轮到你发言了.6) It takes time to do sth .如:It took me an hour to finish reading the novel.读完这本小说花了我一个小时★It替代动名词作主语的常见句型：It’s no good/use doing…如:It’s no use / good crying over spilt milk．覆水难收It’s (well)worth (one’s )while doing/to dosth.It’s worth（your）while to learn english。
学英语是值得的.★It替代主语从句常见句型:1）It is a pity (a shame ,a fact ,a wonder ,a good thing ,good news etc)that……例如：It is a shame that he didn’t pass the exam.很遗憾他没有通过考试。
2）It is strange(natural surprising obvious true good wonderful possible,impossible,likely,unlikely,quite clear.certain ,etc) that…。
例如：It was quite clear that they had no disire for peace.很清楚他们没有和平的诚意。
3）It seems (happened ,turned out, occurred to sb etc.)that…例如：It seemed that things were not as they expected.看起来情况并不像他们所想象的那样。
4）It is said (reported ,decided ,expected ,arranged ,rumoured ,etc)that …例如：It is said that the tickets have been sold out .据说票已售完。
5) It is time that 从句（谓语用过去时）It is time that he went to school.他本该去上学了.6)It seems/appears/sounds/looksas if…….似乎/听起来/看起来….It seems as if it is going to rain.仿佛要下雨了.2当复合宾语中的宾语是不定式、－ing短语或从句，往往用it作形式宾语，而将真正的宾语移至句末，以使句子重心后移。
Do you think it a good habit to read in bed?你认为在床上看书的习惯吗？We find it difficult to learn English well in such a short time．我们认为很难在这如此短的时间内学好英语I will leave it to you to buy the ticket.我要把买票的事委托给你We think it no use crying over spilt milk．我认为木已成舟哭也没用。
Y ou may depend on it that they will support you.你相信好了，他们会支持你的。
They will answer for it that the computer is reliable.他们愿意保证这台电脑是可靠的。
We made it clear when and where we were going to have the meeting．我们宣布了何时何地要举行会议。
I tookit for granted that you would stay with us .我信以为真你要和我们呆在一起.五.It用于强调结构：it没有具体意义，可强调谓语动词外的成分。
其基本句型为：It+be+被强调部分+that(who)+其它……。
★强调主语：主语是人，一般用who （也可用that ）.其他情况用that.。
强调主语用主格；who或that 后面的句子中谓语动词与被强调的主语在数和人称上应保持一致。
例如：It is I who (that) am to blame应付责任的是我。
It was you who didn’t keep your promise。
是你不遵守诺言It was long overwork that made them get tired.长期超负荷的劳动使他们疲被倦不堪。
★强调宾语：当宾语是指人的名词或代词时、强调句中的连接词用whom或that，其他情况用that。
如：It is you that we have been wanting to visit.我们一直想去访问的是你。
★强调状语：被强调的状语可以是时间状语或地点状语，原因状语。
强调句中的连接词只用that例如：It was at that time that I thought of giring him a call.直到那时我才想起要给他一个电话。
It was in the zoo that they saw the elephants.他们是在动物园见的大象。
在运用it引导的强调句时，要注意以下几点：1）强调句的谓语is或was永远用单数，例如：It was yesterday that I met your father in the street．2）不管被强调部分是哪种状语，只能用that连接，不得使用where、when等连词。
例如：It was in the street that I met your father yesterday．3）被强调部分为人时，可用who(主格)和whom(宾格)代替that，用that也行。
例如：It was your father that/whom I met in the street yesterday．It was I that/who met your father in the street yesterday4）强调句中也要注意主谓一致、人称一致和否定转移的问题。
例如：It is they who are our friends．5）not …untill…句型的强调形式为It is/was not untill that 例如:It was not until ten o'clock that we got home last night．6)as since because 均可引导原因状语从句,但是强调句型中只可以强调because从句例如:It was because he was ill that he didn’t come here.7)注意不要混淆强调句和其他从句。