■stop to do sth 的意思是：停下正在做的事去做另一事。此时的stop为不及物动词，其后接的不定式不是宾语，而是状语，表示目的，即为目的状语。如：
I stopped to ask the way. 我停下来问路。
At the top we stopped to look at the view. 到了顶上，我们停了下来眺望景色。
The bus stopped to put down some passengers. 公共汽车停下来让一些旅客下车。
They were tired, so they stopped to have a rest. 他们很累了，所以停下来休息一会儿。
On the way to the station I stopped to buy a paper. 在去火车站的路上，我停下来买了一张报纸。
■stop doing sth的意思是：停止做某事。此时的stop为及物动词，其中的动名词为宾语，是 stop 的对象。如：
It has stopped raining. 雨已经停了。
For an instant his heart seemed to stop beating. 有一会儿他的心脏似乎停止了跳动。
Hearing her husband come in she stopped crying. 听见她丈夫进了来，她就不哭了。
He stopped speaking, and there was not a sound in the room. 他停止讲话，房里一点声音也没有了。
It’s not very easy to stop smoking. 戒烟可不是件容易的事(from www.lulutubu.com)。
When he told us the story, we just couldn’t stop laughing. 他给我们讲完故事后，我们不禁都笑个不停。