虽然他很矮，但是他能跑得很快.

Incorrect english:

Although he is very short, but he can run very fast.

Correct english:

Although he is very short, he can run fast

He is very short, but he can run fast.

解释:

这里的问题是:我们可以用 although 或 but ,但不能同时用，因为这是错误的，其中一个就已经表达了

“虽然...但是...”的意思。

规则是:although 比 but 更正规些。

Examples:

Although I'm tired, I still want to go out and see a movie.

I'm tired, but i still want to go out and see a movie.

Although Nancy does not like her boss, she likes going to work anyway.

Although I asked him not to marry her, he did it anyway. I'm really mad at him.

I asked him not to marry her, but he did it anyway. I'm really mad at him.