初中英语重难点 ｜ 形式主语 it：it 打头阵，真主语殿后

你家孩子是不是一看到 It is important to... 就一脸懵：这个 it 到底指什么？为什么不用 To study hard is important？

这篇只解决一个问题：把形式主语 it，从"看着别扭"升级成"看穿套路"。

01 先弄清出处：这讲的是几年级的知识点？

it 作形式主语是人教版（2024）九年级上册 Unit 2 Inspiring People 的核心语法（It is / was + adj. + (for / of sb) + to do sth.，It is + adj. + that 从句），也是中考单选、完形、写作的高频考点。

适用学段：八年级（初识）、九年级（系统掌握）、中考冲刺均适用。

02 先比较：it 的"真身"与"替身"

一句话：it 放在句首只是"替身"（形式主语），真正的主语在后面（to do / that 从句）。

· 原句（头重脚轻）：To study hard is important.（努力学习很重要。——不定式作主语太长，头重）

· 改写（it 打头阵）：It is important to study hard.（it 形式主语，to study hard 真主语）

判断口诀：看到句首 It is / It seems + 后面有 to do 或 that 从句，it 就是"替身"，真主语在句尾。

03 深度拆解：七个知识点全掌握

知识点一｜It is + 形容词 + to do（做某事是……的）

It is important to study hard.（努力学习很重要。）

It is easy to learn to swim.（学游泳很容易。）

It is dangerous to play with fire.（玩火很危险。）

It is interesting to read story books.（读故事书很有趣。）

It is necessary to keep quiet in the library.（在图书馆保持安静是必要的。）

It is hard to finish the work in one day.（一天之内完成工作很难。）

规律：It is + 形容词 + to do = To do + is + 形容词（不定式作真正主语，it 只是替身避免头重脚轻）。

知识点二｜It is + 形容词 + for sb + to do（对某人来说，做某事是……的）

It is important for us to learn English well.（对我们来说学好英语很重要。）

It is easy for him to pass the exam.（对他来说通过考试很容易。）

It is difficult for me to get up early.（对我来说早起很难。）

It is necessary for students to do sports every day.（对学生来说每天运动是必要的。）

It is helpful for children to read before bed.（对孩子们来说睡前阅读很有帮助。）

It is good for your health to eat vegetables.（吃蔬菜对你的健康有好处。）

规律：for sb 说明"对某人来说"，形容词描述事情本身的性质（important / easy / difficult / necessary 等）——"事情是重要的 / 容易的"，不是"人是重要的"。

知识点三｜It is + 形容词 + of sb + to do（某人做某事真是……）——for / of 核心难点

It is kind of you to help me.（你帮助我真是太好了。）

It is nice of you to say so.（你这么说真是太好了。）

It is clever of her to work out the problem.（她解出这道题真聪明。）

It is silly of him to waste so much money.（他浪费这么多钱真傻。）

It is polite of you to wait in line.（你排队等候真有礼貌。）

It is brave of the boy to save the dog.（这个男孩救狗真勇敢。）

规律：of sb 说明"某人的品质"，形容词描述人的品格（kind / nice / clever / silly / polite / brave 等）——"你是善良的 / 聪明的"；of 结构可改写为 sb is adj. to do：You are kind to help me.

口诀：形容"事情"用 for，形容"人品"用 of。

知识点四｜It is + 名词 + to do / that 从句

It is a good idea to take a walk after dinner.（晚饭后散步是个好主意。）

It is a great pleasure to work with you.（和你一起工作很愉快。）

It is a pity that he missed the train.（他没赶上火车真遗憾。）

It is a fact that the earth moves around the sun.（地球绕太阳转是事实。）

It is my duty to protect the environment.（保护环境是我的责任。）

It is good news that our team won the game.（我们队赢了比赛是个好消息。）

规律：It is + 名词（a good idea / a pity / a fact / my duty）+ to do 或 that 从句，真正主语后置。

知识点五｜It + 动词 + that 从句（It is said that... 据说）——偏难

It is said that he will come back tomorrow.（据说他明天回来。）

It is reported that the meeting was a success.（据报道会议很成功。）

It seems that he is tired.（他似乎累了。——It seems that = He seems to be）

It happens that I have the same book.（碰巧我有同样的书。——It happens that = I happen to have）

It is believed that the story is true.（人们相信这个故事是真的。）

It is known that he is a good teacher.（众所周知他是个好老师。）

规律：It is said / reported / believed / known + that 从句表"据说 / 据报道 / 人们相信"；It seems / happens + that 从句表"似乎 / 碰巧"——都可改写为"人 + seem / happen + to do"。

知识点六｜形式宾语 it：find / think / make + it + 形容词 + to do（偏难）

I find it important to learn English.（我发现学英语很重要。——it 形式宾语，to learn 真宾语）

She thinks it easy to finish the work.（她觉得完成工作很容易。）

We find it interesting to play chess.（我们发现下棋很有趣。）

The rain made it impossible to go out.（下雨使我们不可能出门。）

He found it hard to say goodbye.（他发现说再见很难。）

I think it necessary to tell him the truth.（我认为有必要告诉他真相。）

规律：动词 find / think / make + it（形式宾语）+ 形容词 + to do（真正宾语）——与形式主语同思路，只是 it 放到宾语位置。

知识点七｜易错点：四个"要命"的坑

It is important that we learn English well.（√）vs It is important that do we learn...（×）——that 从句必须用陈述语序。

It is kind for you to help me.（×）→ It is kind of you to help me.（√）——kind 描述人的品质，用 of。

It is raining now.（下雨了。——这里 it 是"真主语"，指天气，不是形式主语）

It is 8 o'clock now.（现在八点。——it 指时间，真主语）

It is two kilometers from here to school.（从这里到学校两公里。——it 指距离，真主语）

It is difficult to learn Japanese.（学日语很难。——it 形式主语，真正主语 to learn）

规律：四个坑分别是——that 从句陈述语序、kind 类人品形容词用 of、天气 / 时间 / 距离的 it 是真主语不是形式主语、形式主语后面必须有 to do / that 从句作真正主语。

04 配套练习：10 题精练

一、单项选择（1—8 题）

1. ___ is important to study hard. A. This  B. That  C. It  D. He

2. It is easy ___ him to pass the exam. A. for  B. of  C. with  D. to

3. It is kind ___ you to help me. A. for  B. of  C. with  D. to

4. It is a pity ___ he missed the train. A. that  B. what  C. which  D. who

5. ___ is said that he will come back tomorrow. A. This  B. That  C. It  D. He

6. I find ___ difficult to learn Japanese. A. this  B. that  C. it  D. them

7. It is necessary ___ students to do sports every day. A. for  B. of  C. with  D. to

8. It is clever ___ her to work out the problem. A. for  B. of  C. with  D. to

二、用 for 或 of 填空（9—10 题）

9. It is important ___ us to keep healthy.

10. It is polite ___ you to wait in line.

05 参考答案与解析

1. C。It is + 形容词 + to do，it 作形式主语。

2. A。easy 描述"事情的性质"，用 for sb。

3. B。kind 描述"人的品质"，用 of sb。

4. A。It is a pity that + 从句，that 引导真正主语从句。

5. C。It is said that 据说，it 作形式主语。

6. C。find + it + 形容词 + to do，it 作形式宾语。

7. A。necessary 描述事情性质，用 for sb。

8. B。clever 描述人的品质，用 of sb。

9. for。important 是事情性质，用 for。

10. of。polite 是人的品质，用 of。

06 加分考点：三个延伸用法

· for / of 判断法：把 sb 还原成主语试读——"sb is + 形容词"成立用 of（You are kind），不成立用 for（*You are important，×，所以用 for）。

· It is said / reported / believed that：中考阅读高频"据说 / 据报道"，改写为被动 + 形式主语——It is said that he is rich. = People say that he is rich.

· 形式宾语三动词：find / think / make + it + 形容词 + to do——I think it necessary to take notes.（我认为记笔记有必要。）

写在最后

形式主语 it 不是"莫名的 it"，而是"替身"：it 打头阵，真主语（to do / that 从句）殿后；形容事情用 for、形容人品用 of；It is said that 是"据说"；find / think / make 后面还能接形式宾语 it。

你最容易栽在哪个形式主语上？欢迎把错题发到评论区，下期我们继续拆。