爱华网It作形式主语是中学阶段英语学习的主要语法项目之一，因此要懂得如何使用，以下是由爱华网小编整理关于形式主语it的用法的内容，希望大家喜欢!
形式主语it的用法当不定式(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。
e.g. It is wrong to tell a lie.
(说谎是错误的。) 〔It为to tell a lie的形式主语〕
It is no use arguing about it.
(争吵是没用的。) 〔It为arguing about it的形式主语〕
It is uncertain who will come.
(谁要来还不确定。) 〔It为who will come的形式主语〕
It 作形式主语的常见句型：
① It + be + 形容词 + to do sth. / doing / that ….
e.g. It is very important to learn a foreign language.
(学一门外语非常重要。)
It is useless crying over the spilt milk.
(覆水难收。)
It was really surprising that she married a man like that.
(她嫁给那样的男士真让人惊讶。)
② It + be +名词词组 + doing / that ….
e.g. It is no good telling lies.
(撒谎没好处。)
It is a pity that you didn’t go to see the film yesterday.
(你昨天没看成那部电影真遗憾。)
It is a truth that there would be no new China without the Communist Party.
(没有共产党就没有新中国，这是毋庸质疑的。)
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.
e.g. 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。)
It is believed that China will become one of the strongest countries in the world.
(大家都相信中国将会步入世界强国之列。)
It was reported that more than 170 thousand people died in the 2004 tsunami.
(据报道，至少有十七万人在2004年那场海啸中丧生。)
④ It + seems / appears / happens等不及物动词 + that ….
e.g. It seems that he enjoys pop songs very much.
(似乎他非常喜欢流行歌曲。)
It appears that Tom might change his mind.
(看来汤姆可能会改变主意。)
⑤ 若句子是疑问形式，就只能用it作形式主语。
e.g. Does it matter much that they won’t come tomorrow?
(他们明天不来很重要吗?)
Is it true that he will go abroad next week?
(他下周出国是真的吗?)
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。
e.g. 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 took him fourteen hours to go to New Zealand from Shanghai by plane.
(从上海乘飞机去新西兰花了他14小时。)
How long does it take you to go to Beijing from Qingdao by train?
(从青岛坐火车到北京一般要花多久时间?)
I am not sure, but I think it takes at least nine hours to get there.
(我不能肯定，但估计至少要九个钟头才能到那儿。)
