有两种结构：
1.动名词短语 + 系动词 + 表语，如：Seeing is believing. 眼见为实
2.形式主语+ 系动词 + 表语 + 动名词短语，如：It is helpful keeping exercises every day. 每天坚持锻炼是有好处的。
一般来说动名词或动名词短语作主语，放在句首。
e.g. Learning a foreign language is very useful to everyone.
Reading in bed is bad for your eyes.
做宾语的结构：
动名词及其短语放在行为动词介词后，作宾语。
e.g. Have you finish doing your homework ? (动词宾语)
He is not good at making friends. (介词宾语)
注意事项：
1. 动名词作主语表单数概念，谓语动词用单数形式。
e.g: Walking after supper is good for your health.
2. 动名词作动词宾语，往往是一些固定搭配，常跟动名词作宾语的动词有：finish, enjoy, mind, practise, deny, consider, suggest, admit, put off, insist on等。
3.动名词的复合结构作主语和宾语
什么是动名词的复合结构？指物主代词、名词所有格是动名词逻辑上的主语、动名词是其逻辑上的谓语。
(1)动名词复合结构作主语
e.g. Your coming made us happy.
Your father’s cooking is very good.
(2) 动名词的复合结构作宾语
e.g. Do you mind my smoking ?
My friend insisted on my staying here.
有两种结构，
动名词短语 + 系动词 + 表语，如：Seeing is believing. 眼见为实
形式主语+ 系动词 + 表语 + 动名词短语，如：It is helpful keeping exercises every day. 每天坚持锻炼是有好处的。