动词不定式在句子中可做任何成分，但不能做谓语。

(1）动词不定式做主语

eg: To swim with you was very enjoyable.

注：动名词和动词不定式均可以做主语和表语，但动名词表示经常性的，抽象的动作，而不定式表示特指的一次性的具体的动作。

(2）动词不定式做表语

eg: Her wish is to become a teacher.

注：表语为不定式时，主语也是不定式；当主语部分含有动词do时，做表语的不定式可以省略to.

eg: To see is to believe.

All you have to do is (to) study hard.

(3) 不定式做宾语

以下及物动词后常用动词不定式：

want,decide,aim(目标),manage(试图),hope,ask,happen,like,love,choose,prevent(阻止),promise,continue,plan,learn,fail等。

eg: I decide to look for a job.

(4) 动词不定式做定语

动词不定式做定语往往要后置，与被修饰词之间存在动宾关系、主谓关系、同位关系和修饰关系。如果动词不定式是不及物动词，应该在动词后加上适当的介词。如果被修饰词是地点、时间、方法，通常省略动词不定式后的介词。

eg: I have something to say.(动宾关系）

I was the last one to leave here.(主谓关系）

I have no wish to quarrel with you.(同位关系）

This is the best way to do that.(修饰关系）

I have nothing to worry about.(不及物动词后加介词）

I can't find a place to play (in).(省略介词in)

注：当名词用特定的定语如：frist,last,next,only等以及形容词最高级修饰时，后面用不定式修饰。

eg: He is the only person to know the truth.

(5）不定式做状语

不定式做状语主要表达结果、目的和原因。

eg: He worked day and night to play for the debts.(目的状语）

He woke up to find everyone gone.(结果状语）

We laughed to hear the news.(原因状语）

注：动词不定式与only连用时，可表出乎意料的结果。

eg: He went to seaside only to be drowned.

(6) 动词不定式做补语

eg: Allow me to introduce her to you.

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