一．代词it的用法：

Ａ：用于指代this,that或前面提到或对方心目中的人或事物．

例：What's this in English?-----It's a pen.

B:在性别，身份不详时指人或指婴儿．

例：Someone is knocking at the door.Who can it be?--------It's me.

C:表示时间　距离　温度　环境　天气等自然现象．

例：It's quite warm for january,isn't it?( 表天气）

      It's about a quarter's ride from here to the train station.(表距离）

二．引导词it 的用法：

A:作形式主语，代替由动词不定式短语　动词+ing形式短语或名词性从句所表示的真正的主语，常用结构有：

★. It's + adj./n. + for/of sb. to do sth.

★. It's + adj./n. + doing sth.

★. It's + adj./n. + clause.

★. It's + p.p. + clause.

B:作形式宾语，代替由不定式短语，动词－ing形式短语或名词性从句所表示的真正的宾语，常用结构有：think/consider/feel/take/make,etc. +it +adj./n. + to do sth./doing sth./clause.

C:表模糊概念，指代后面从句所叙述的内容，常用于此结构的动词有：like,dislike,hate,love,see to,depend on/upon,appreiate等 .  如：I hate it when people laugh at the disable.　　　

D:用于强调句中：It is/was + 被强调部分　＋　that/who/......

注意：此强调结构通常强调　句中的主语，宾语，宾补或状语．被强调部分指人时可用that或who,强调其他内容时，一般只用that.

例：1.It was in the park that I met my old friend yesterday.　

      2.It was I who/that was to biame for the accident.