英语什么时候用doing什么时候用to do?

？

用作介词的to

to 有两种用法： 一为不定式+动词原形； 一为介词+名词/动名词, to 在下面的用法中是第二种，即to+ 名词/动名词：

admit to承认， confess to承认，
be accustomed to 习惯于， be used to 习惯于， stick to 坚持， turn to开始，着手于， devote oneself to 献身于， be devoted to 致力于， look forward to 盼望， pay attention to 注意

省to 的动词不定式

1） 情态动词 ( 除ought 外，ought to)：
2） 使役动词 let, have, make：
3） 感官动词 see, watch, look at, notice , observe, hear, listen to, smell, feel, find 等后作宾补，省略to。

注意：在被动语态中则to 不能省掉。
I saw him dance.
=He was seen to dance.
The boss made them work the whole night.
=They were made to work the whole night.
4） would rather，had better：
5） Why… / why not…：
6） help 可带to，也可不带to, help sb (to) do sth：
7） but和except：but前是动词do时，后面出现的动词用不带to的动词不定式。
8） 由and, or和than连接的两个不定式，第二个to 可以省去：
9） 通常在discover, imagine, suppose, think, understand等词后，可以省去to be：
He is supposed (to be) nice. 他应该是个好人。

举例：
He wants to move to France and marry the girl.
He wants to do nothing but go out.

比较： He wants to do nothing but go out.
He wants to believe anything but to take the medicine.

助动词do 的用法

1） 构成一般疑问句，例如：
Do you want to pass the CET? 你想通过大学英语测试吗？
Did you study German? 你们学过德语吗？

2） do + not 构成否定句，例如：
I do not want to be criticized. 我不想挨批评。
He doesn't like to study. 他不想学习。
In the past, many students did not know the importance of English. 过去，好多学生不知道英语的重要性。

3) 构成否定祈使句，例如：
Don't go there. 不要去那里。
Don't be so absent-minded. 不要这么心不在焉。
说明： 构成否定祈使句只用do，不用did和does。

4） 放在动词原形前，加强该动词的语气，例如：
Do come to my birthday party. 一定来参加我的生日宴会。
I did go there. 我确实去那儿了。
I do miss you. 我确实想你。

5） 用于倒装句，例如：
Never did I hear of such a thing. 我从未听说过这样的事情。
Only when we begin our college life do we realize the importance of English.
只有在开始大学生活时我们才认识到英语的重要性。
说明： 引导此类倒装句的副词有never, seldom, rarely, little, only, so, well等。

6） 用作代动词，例如：
---- Do you like Beijing? --你喜欢北京吗？
---- Yes, I do. --是的，喜欢。（do用作代动词，代替like Beijing.）
He knows how to drive a car, doesn't he?
他知道如何开车，对吧？




动名词作主语、宾语和表语

1）作主语
Fighting broke out between the South and the North.
南方与北方开战了。

2）作宾语

a. 动词后加动名词doing作宾语 V. + doing sth
admit 承认 appreciate 感激,赞赏 avoid 避免
complete 完成 consider 认为 delay 耽误 deny 否认 detest 讨厌 endure 忍受 enjoy 喜欢 escape 逃脱 prevent阻止
fancy 想象 finish 完成 imagine 想象 mind 介意 miss 想念 postpone 推迟 practise 训练 recall 回忆 resent 讨厌 resist 抵抗 resume 继续 risk 冒险
suggest 建议 face 面对 include 包括 stand 忍受 understand 理解 forgive 宽恕 keep 继续

举例：
(1) Would you mind turning down your radio a little, please?
(2) The squirrel was lucky that it just missed being caught.

b. 词组后接doing
admit to prefer…to be used to lead to devote oneself to object to stick to busy look forward to(to为介词）

no good, no use, It's worth…, as well as,
can't help, It's no use /good be tired of
be fond of be capable of be afraid of
be proud of think of / about hold off
put off keep on insist on count on / upon
set about be successful in good at take up
give up burst out prevent … from…

3）作表语
Her job is washing，cleaning and taking care of the children.

这和动词有关 语法书上会有详解

一些词语只能接不定式 有的却只能接现在分词

还有一些词语接不定式 表去做 接分词 表做过

还要认真记忆

一般来说，to do表目的，doing表伴随和主动，二者都可以做后置定语。