Question

英语动词不定式在句子中用法？

We think it important to learn English.这个句子是不是可以说成 We think to learn English important.
上面的important做什么成分？为什么不用在important前面加is呢？

Answer 1

这里it作形式宾语，因为实际的宾语是不定式短语，不定式短语过长，所以后置，语法句子结构上和谐一点。

而important作宾语补足语，补充说明宾语(也就是不定式短语)。如果在important前面加is，那么it就变成从句中的形式主语了,后面的不定式作真正的主语，而后面整体就是一个做think的宾语从句，省略了引导词that.

We think (that) it is important to learn English.

Answer 2

回答如下：
问题1：本句不可以改成“We think to learn English important”, 但可以改成“We think it is important to learn English”, 或者“We think it (is ) important that we (should) learn English”。
动词think的用法：
think + 宾语 (+ to be )+ 宾补(形容词、名词) ; think to do ; think + 疑问词+ 不定式; think + 宾语从句; think + 形式宾语it + 宾补(形容词、名词) + 真正的宾语(逻辑宾语)不定式; think + 形式宾语it + 宾补(形容词、名词) + 真正的宾语(逻辑宾语) that从句。例如：
I think to leave here.
You should think what to do next.
We think him (to be )a doctor.
He thinks the question(to be ) too hard.
I think (that) he is too young to join the army.
I think it difficult to work out this problem.
We think it necessary that we should do the experiment.

Answer 3

1. 不能说成We think to learn English important. 但只要在important前加上is就对了，即

We think (that) to learn English is important.

2. 题主所给原句中，形容词important作形式宾语it的补语，不定式短语to learn English是真实宾语。

Answer 4

动词不定式，可以相当于名词，形容词或副词的功能。所以动词不定式可以在句子中可以充当主语，宾语，表语，宾语补足语，定语和状语。也就是说，动词不定式可以充当除了谓语以外的所有句子成分

Answer 5

这个句子主语是We，think是谓语动词，it是形式宾语，important是宾补，真正的宾语是to learn English(不定式短语做真正的宾语)。