It 用作形式宾语：当不定式（短语）、动名词（短语）或从句在某个句子中作宾语时，为保持句子结构平衡，避免句式结构的混乱，常用it作形式宾语，而将真正的宾语放在句尾。此时it仍只起先行引导作用，本身无词义。it 作形式宾语多用于下列句型中。
1、当不定式（短语）、动名词（短语）或从句在复合宾语结构中作某些动词的宾语时（如think, make, find, consider, feel, suppose等）。例如：
They found it pleasant that they worked with us Chinese.他们发现与我们中国人一起工作很愉快。
I don’t feel it difficult to understand the Special English.我觉得理解英语特别节目并不难。
He makes it a rule never to borrow money. 他立志决不向别人借钱。
I think it no need talking about it with them. 我认为没必要跟他们谈。
2、某些表示“喜、怒、哀、乐”的动词，如like, enjoy, love, hate等，往往不能直接接宾语从句。例如
I don’t like it that he’s so lazy. 我不喜欢他那么懒惰。
I hate it when my mother asks me to eat eggs. 我讨厌母亲要我吃鸡蛋。
3、that引导的宾语从句不能直接作介词的宾语。例如：
You may depend on it that we shall always help you.尽管放心，我们会随时帮你的。
Would you see to it that she gets home early? 你负责保证她早到家，好吗？
He insisted on it that he was innocent. 他坚持说自己是无辜的。
4、由及物动词与介词组成的固定搭配中，宾语从句若作该动词的宾语时，须借用it。例如：
I leave it to your own judgement whether you should do it.我让你自己判断这事是否该做。
We owe it to you that there wasn’t a serious accident.多亏了你才没有发生严重事故。
扩展资料：
It除了用作代词表示指代意义以外，还可以用作形式主语，It 用作形式主语：
1、当不定式（短语）、动名词（短语）或从句在某个句子中作主语时，为保持句子结构前后平衡，避免头重脚轻，因此常用it作形式主语置于句首，而将真正的主语放在句尾。此时it只起先行引导作用，本身无词义。例如：
It is wrong to tell a lie. 说谎是错误的。
2、It 作形式主语的常见句型
It + be + 形容词 + to do sth. / doing / that ….。例如：It is very important to learn a foreign language. 学一门外语非常重要。
It + be +名词词组 + doing / that ….，例如：It is no good telling lies. 撒谎没好处。
3、It + be + 过去分词 + that ….：该句型常见动词有：say, hope, think, suppose, expect, report, know, believe, decide, etc.。例如：
It is said that they have invented a new type of computer. 据说他们发明了一种新型电脑。
4、It + seems / appears / happens等不及物动词 + that ….。例如：It seems that he enjoys pop songs very much.似乎他非常喜欢流行歌曲。
5、若句子是疑问形式，就只能用it作形式主语。例如：Does it matter much that they won’t come tomorrow? 他们明天不来很重要吗？
6、It + takes + (sb.) + some time + to do sth.这是一个表示“（某人）花多少时间干某事”的句型，其中it是形式主语，代替后面的不定式（to do sth.），句型中的sb.也可以省略。例如：
It took me some time to read the reading materials.我花了一些时间才读完那段阅读材料。
it作形式宾语的句型
通常和下列动词连用：
consider, think, make, find, believe, count, declare, deem, fancy, feel, guess, imagine, judge, prove, see, show, suppose, understand, take等。例如：
● We consider it our duty to support good leaders.
● I think it best to get along well with others.
● The new method makes it possible to complete the task faster.
● Tom found it very embarrassing to be reminded of the long-standing debt.
● Susan deemed it advisable to keep the matter secret.
● We all feel it nice to be able to visit that distinguished university.
● Who can prove it wrong to have a "make-money-quick" mentality?
