因為it是代詞，所以放在中間。look it up是動詞look和副詞up構成的短語，代詞應放在兩詞中間；名詞可放中間，也可放再後面。類似短語：try it on,pick it up,give it up等。
雙語例句
1、"Look it up." and he walked out.
"查壹下，"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.
我壹時想不起這個名字，不過我可以給妳查壹查。
4、If you know the author only, just look it up in the author catalogue.
如果妳只知道著作人，那就查作者目錄。
5、Why don't you look it up in the encyclopedia?
妳為什麽不去查百科全書？