英语中形容词比较级在做定语时需要加than引导的比较状语从句吗?

不一定.下面的都是比较级作定语的情况：
1)Which do you prefer,the bigger one or the smaller one?
2)There are two lamps in the room.The brighter lamp is made in Japan.
又可以：The car which is newer than that one belongs to Tom.
所以,用不用than要看一定的语境决定.

不一定。

The girl who is in red is more beautiful than the one who is sitting on the grass.
你想表达什么，你也可以说一句话，你自己写个句子看看？