It 作替代词充当主语和宾语的用法归纳：

 

一、it作形式主语

（一）、it用作形式主语可以代替下列从句：

1.由 that引导的主语从句

It is quite clear that he has read the book. 很显然，他读过这本书。

2. 由what引导的主语从句

It doesn’t matter what he says. 他说什么没关系。

It was clear enough what he meant. 他的意思是很明显的。

3. 由who引导的主语从句

It hasn’t been decided who will be sent to work there. 还没决定将派谁到那里工作。

4. 由how引导的主语从句

It struck her how gentle he was being. 她深深感到他多么温存。

5. 由when引导的主语从句

It hasn’t been made clear when the conference is to take place. 会议什么时候召开还没有宣布。

6. 由where引导的主语从句

It’s not known where she went. 她到哪里去了没人知道。

It did not matter much where he lived. 他在哪里住都没有关系。

7.由 why引导的主语从句

It was clear why he had asked for a conference. 他为什么要求召开会议原因很清楚。

8. 由whether引导的主语从句

It makes little difference whether we go or stay. 我们去还是留没有多大差别。

It’s not yet settled whether I am going to America. 我去不去美国还没定。

（二）、it用作形式主语有用的句式：

1. 用于it seems (appears) that…句式。如：

It seems that he knows everything. 他好像什么都知道。

It appears that we may be mistaken. 看来我们可能弄错了。

但是，英语一般不说it looks that…，可改用it looks as if…。如：

It looks as if we’ll be late. 我们似乎要迟到了。

2. 用于it happens (occurs) that…句式。如：

It happened that I was standing next to him when he collapsed. 他倒下时我恰巧站在他旁边。

It didn’t occur to him that she would refuse his invitation. 他没有想到她会拒绝他的邀请。

3. 用于it follows that…句式。如：

He is wrong, but it does not follow thatyou are right. 他错了，但并不能由此推断你是对的。

She’s not in the office but it doesn’t necessarily follow that she’s ill. 她不在办公室, 并不见得就是病了。

（三）、it用作形式主语代替动名词的用法主要见于以下句式：

1. It is no use (no good, fun, great fun, a new experience, a great honour, etc) doing sth。如：

It is no good talking. 空谈是没有用的。

It’s fun working for him. 为他工作很有意思。

It’s great fun sailing a boat. 扬帆驾舟十分有趣。

 

2. It is good (nice, useless, interesting, pleasant, tiring, etc) doing sth。如：

It is useless speaking. 光说没有用。

It was pleasant sitting there. 坐在那里很愉快。

It’s so nice sitting here with you. 和你坐在一起真是愉快。

3. it is worth while doing sth。如：

It’s worth while doing the work. 这项工作值得做。

Do you think it’s worth while quarrelling with me? 你认为和我吵值得吗?

4. 其他句式。如：

It doesn’t matter wasting a little money. 浪费一点钱没有关系。

It felt funny being dressed like a peasant girl. 打扮成村姑感到有点怪怪的。

What’s it like being married? 结婚是什么味道。

 

二、it用作形式宾语

 （一）、it 作形式宾语代替宾语从句。主要有如下几个句型：

1. 动词+ it + that-从句。能用于此结构的动词常见的有 have, take, put, like 等，如：

I like it that you came. 你来了，我很高兴。

I take it (that) he will come on time. 我认为他会准时来的。

You can put it that it was arranged before. 你可以说这是以前安排的。

Rumor has it that the defence minister will soon resign. 据传闻，国防部长不久就要辞职。

2. 动词 + it + when (if)-从句。能用于此结构的动词常见的有 enjoy, hate, love, like, dislike, appreciate, prefer 等。如：

I dislike it when you whistle. 我不爱听你吹口哨。

We really appreciate it when she offered to help. 她来帮忙了，我们十分感激。

I’d prefer it if I didn’t have to do so much work. 要是我不必做那么多工作，好就太好了。

3. 动词 + prep + it + that-从句。能用于此结构的动词不多，常见的有see to, look to, insist on, stick to, depend on, answer for 等，如：

See to it that you’re not late again. 注意千万不要再迟到。

Look to it that this doesn’t happen again. 注意不要再发生这种事。

I can’t answer for it that he will come. 我不能保证他会来。

You may rely on it that he’ll come to meet you. 你放心，他会来接你的。

4. 动词 + it + 介词短语+ that-从句。能用于此结构的动词不多，常见的有take it for granted, bring it to sb’s attention, owe it to sb 等。如：

I owe it to you that I am still alive. 多亏有你我才仍然活着。

I took it for granted that he would help us. 我认为他会帮助我们的。

（二）、当不定式、动名词等复杂成分用作宾语且其后跟有宾语补足语时，通常会在宾语补足语前使用形式宾语it，而将真正的宾语移至句末，其基本结构为“动词+it+宾语补足语+不定式(动名词或从句)”。如：

I find it difficult to do the job well. 我发现做好这件事不容易。

I think it best that you should stay here. 我认为你最好住这儿。

We think it no use complaining. 我们认为抱怨是没有用的。