因为it是代词，所以放在中间。look it up是动词look和副词up构成的短语，代词应放在两词中间；名词可放中间，也可放再后面。类似短语：try it on,pick it up,give it up等。
双语例句1、"Look it up." and he walked out.
"查一下，"他走了出去。
2、Look it up in the index.
在索引中查找。
3、I can't remember the name off the top of my head, but I can look it up for you.
我一时想不起这个名字，不过我可以给你查一查。
4、If you know the author only, just look it up in the author catalogue.
如果你只知道著作人，那就查作者目录。
5、Why don't you look it up in the encyclopedia?
你为什么不去查百科全书？
