look at表示“看，考慮”的意思；look up表示“查字典，拜訪，仰望”的意思。雖然都是look 和介詞組成的詞組，但是兩者在含義上有很大的區別。
look at 動詞詞組， 表示“看；考慮；著眼於”。
1）看；朝…看；盯
The children looked at their new teacher in curiosity.
孩子們好奇地望著新老師。
2）看待；認為：
We should learn to look at problems all-sidedly.
我們應該學會全面看問題。
3）考慮;著眼於;接受[常用於 will(或 would) not look at]:
The manager will not look at a report like that.
經理不會答理那樣壹份報告。
4）檢查；察看：
You should look at that house before you decide to buy it.
妳應該看看那棟房子再決定購買。
5） 過目；瀏覽：
Have you looked at their report?
妳看過他們的報告了嗎?
2、look up 動詞詞組，表示“仰望；查閱；尊敬；拜訪”的意思。
1）查詢，查看
It is unnecessary to look up every word you don’t know in the dictionary while your are reading.
閱讀時,碰到生詞,不必都要在詞典中查閱。
2）擡頭看，好轉
I looked up and saw him.?
我擡起來看見了他.?
The national economy is beginning to look up.?
國民經濟正在開始好轉.?