请看下面的几句:

He is taller than me/I.

=He is taller than I am.

He sings better than she/her.

=He sings better than she does.

He swims faster than I/me.

=He swims fastet than I do.

关键是看than比较状语从中的谓语动词是否省略；其谓语动词是否是be动词还是其它动词，是什么时态；还看其主语是几人称和单复数等。