首先，你的句子下列句子是错误的：

I spend more time on looking up the dictionary than reading the book.

应改为：

I spend more time (in) looking up words in the dictionary than reading the book.

look sth up 或 look up sth 这个短语动词中，look 为及物动词，up为副词。look up sth 意为： to search for (something) in a reference book, on the Internet, etc.

• If you don't know what a word means, you should look it up (in the dictionary).

• look up a telephone number

• look up an article in the encyclopedia

汉语查词典，不能翻译为look up the dictionary, 而应根据逻辑意义——在词典中查某个词的意义，翻译为 look up a word in the dictionary.

look up sth中的up为副词，意为：so as to appear or be present。这里up为作为结果出现的意思，而不是向上、在高处的意思。

• The missing ring turned up. [=the missing ring was found]

• They never showed up.

• Houses were going up quickly.

look up to sb 意为respect or admire sb 的意思。此时 up为向上的意思，向上看引申为仰视，则有了尊敬、崇拜的意思了。

所以，动词短语意义的变化，都是从动词或副词、介词的本义的引申而来。你要追究词义的变化，就需要仔细研究有关词的本义，而不是闭上眼睛凭空想像。