非谓语动词历来是高考中的重点，不定式结构在考点中常占很大比重。用法也很复杂，现就动词不定式to 的几种常见的省略形式作如下小结。

1．感官动词和使役动词在主动语态中不需要带to，即我们常说的“一觉二听三让五看”：feel,　listen to 、hear ,let、make、have, see、watch、notice、observe、look at.

The teacher has us keep a diary every day.

老师要我们每天写一篇日记。

He noticed Mary take a branch of flowers in her hand.

　　他注意到玛丽手中拿着一束鲜花。

注意：　除let 外其他在变成被动语态时要加上to。

The lady was seen to enter the hotel by us .

　　我们看见那个女人进了那家酒店。

2　由 all， what 引导的主语从句或者主语被only, first, one, least 或形容词最高级修饰时，而且从句中含有do时，其表语如果是动词不定式，则往往省去to。

What she wanted to do was drive all night.

她想做的是彻夜开车。

the only thing she could do was go to the furniture shop to buy a new bookshelf.

她能做的只是去傢具傢具行买了一个全新的书架。

All I did was empty the kettle.

我所做的是倒空这个壶。

3．不定式做help后的宾语补足语或宾语时，可带to也可不带。

Can I help（to） carry it for you?

我可以帮你搬吗？

I helped him（to）fix the car.

我帮助他修车。

4．常用的结构　may well do，may as well do (还是…好了)及but或except后接不定式时，如果它们前面有do便可省略to，其结构为can not do but…，can not help but…等句型，

You might as well have a try.

你何妨试一试。

She can do nothing but laugh bitterly.

她除了苦笑，不知道可以做些什么。

There is nothing he could do but play all day long。

他除了整天玩，别无它事可做。

5．在had better，would rather，rather than之后省略to。

You'd better not tell him the news .　

你最好不把这个消息告诉他。

Rather than wait anyone, I decided to go home by bus.

我决定乘公交回家而不愿等候任何人。

6. 由并列连词and，except, but, than, or 连接两个以上的具有相同意义或功能的不定式时，第二个动词不定式不带to。

I’d like to stay with you, help you and learn from you.

我想留下和你一起呆着，帮助你并且向你学习。

The boss told us to stay there and wait till he came back.

l老板告诉我们呆在那里一直等到他回来。

注：如果两个不定式表示对照或对比时，则不能省略to.

He hasn′t decided whether to leave or to stay.

他还没有决定是去还是留。

To try and fail is better than not to try at all.

尝试而失败也比不尝试好。

7. 通常在discover, imagine, suppose, think等词后作宾补时，可以省去to be。例如：　

She is supposed （to be） kind.　她应该是个好人。

8. 以Why或Why not 开头表请求的结构中常跟上动词原形,省略to。

Why not go out for dinner?

为什么不出去吃晚饭呢？