1. see sb doing “看到某人正在做某事”，强调只看到了动作的部分过程。

I saw him playing basket on the playground.
2. see sb do “看见某人做了某事”，强调看到了动作的全过程(要注意这里的do 是省略to的不定式)

I saw him go into that room.

如果变为被动to不省略

He was seen to go into that room.

3. see sb done 表宾语和动词之间是被动的关系。