一、概述
1、主语（Subject）S+动词（Verb）V形成句子。
John works hard。
2、主语省略变成祈使句。
Work hard=（You should) work hard.
注意：祈使句变否定形式时，要在原形动词前加Don't
Don't fool around.
二、可做主语的词类
名词、带刺、动名词、不定式短语、名词性从句、名词短语、表距离的地点副词短语等都可做主语
1、名词作主语
The child is apt（喜欢） to tell lies.
2、代词作主语
He always keeps his promise.
3、动名词或不定时短语作主语
Seeing him makes me angry.
To see him is my purpose of coming here.
a、动名词作主语（表示已知的事实或曾经做过的经历。）
Listening to music makes my happy.
b、不定式作主语（表示一种意愿、目的或者未完成的事情）
To study abroad is my greatest desire.
To go to Japan for a visit is my paln for this year.
注意
不定式与动名词做主语，会出现主语太长的现象，常用带刺 It作形式主语，置于句首，真正主语移至句尾。动名词移至句尾厂改为不定式。
Collecting stamps is one of his hobbes.
=It is one of his hobbies to collect stamps.
以下例外：
It is no use + 动名词短语 = It is useless + 不定式短语 = It is of no use + 不定式短语 = There is no use/sense/point in + 动名词短语
It is useless to cry over spilt milk.（覆水难收）
4、名词性从句做主语
a、句子决不能当主语，变成名词性从句方可作主语
That he doesn't study English makes me angry.
b、名词性从句的种类：宾语从句，主语从句，表语从句，同位语从句。
1）、That从句
That he doesn't believe my words
2）、whether从句
a）、问句有be动词
Is he happy?
--》Whether he is happy.
b)、问句中有一般助动词（can,will,may,should,ought to,must,have）
can he do it?
--》Whether he can do it.
c)、问句中有do，dose，did等助动词
Did he come?
--》whether he came.
3）、疑问词所引导的从句
由when，what,how,where,why引导而成
a)、问句中有be
What is he doing？
--》what he is doing
b)、问句中有一般助动词
Where can he find it?
--》Where he can find it.
c)、问句中有do，dose，did等助动词
What did he write?
--》what he wrote
注意：who，which，what在疑问句中作主语，变名词性从句时，结构不变。
Who came here?
--》who came here
c、名词性从句的功能
名词性从句可做主语、宾语或在be动词之后做表语
1）、做主语
That honesty is the best policy is a proverb（谚语） (which) we should keep in mind.
（“诚实为上策”是一句我们应该时刻谨记于心的箴言）
注意：
与动名词与不定式一样，名词性从句做主语也会主语过长，同样可用It
It is a proverb we should keep in mind that honesty is the best policy.
2）、做及物动词的宾语
transitive verb（vt.）=及物动词，Object（O.）=宾语
I know that he will go abroad in the near future.
3)、名词性从句作介词的宾语：
preposition（prep.）=介词
a)、仅可用whether和疑问词从句，不可用that从句
I am worry about whether he can do it.
b)、遇有介词，一定要用that从句时，不久如下
（1）、介词+the fact+that 从句
the fact 作介词宾语，that从句变the fact的同位语
I am sure of the fact that the team has won the game.
（2）、保留介词，不加the fact，that从句作如下变化：
第一步：除去that
第二步：that的主语变成所有格
第三步：动词变动名词
I am worry about his playing around all day
注意：
（a）、that 从句若有do，does，did，丢弃即可。
（b）、that从句若有will或would助动词，丢弃即可
（c）、从句若有一下助动词作以下变化
may--> be likely to
can-->be able to
I am happy about his being able to do it
（3）、be+adj.+that, 即去掉介词，that 从句放在形容词后面，作其宾语。
I am sure that the team has won the game .
注意：
a）、（1）和（3）最为普遍，（2）考试多
b）、有时介词亦可直接接that从句，形成惯用句
in that=because
except that 只可惜，除了。。。
notwithstading that 尽管
=despit the fact that
=in spite of the fact that
Notwithstanding that he is nice,i don't like him.
5、名词短语做主语
名词系短语由“疑问词+不定式短语”形成
a、疑问副词
where to live
whether to try again
when to talk to him
how to do it
b、疑问代词
what to do
whom to see
which to buy
whom to talk to
注意：
1)、疑问副词是副词的性质，不做不定式短语中及物动词的宾语，引文代词有名词的性质，可以做不定式短语中及物动词的宾语
故 what，whom，which 名词短语中 可做do，see，buy，to（介词）的宾语
2）、名词短语有名词性质，亦可作主语
Where to meet him is not decided yet.
6、表距离的地点副词短语作主语
from +地方名词+to+地方名词
From Shanghai to Beijing is about 1000 kilometers.
It is about 1000 kulometers from Shanghai to Beijing