According to the Oxford Advanced Learner's English-Chinese Dictionary, idiom means a group of words whose meaning is different from the meanings of the individual words. According to Longman Dictionary of English Idioms (Longman Group itd.1979). strickly speaking, idioms are expressions that are not readily understandable from their literal meanings of the individual elements. It includes set phrases, proverbs, sayings and maxims. Every nation has its own idioms, and idioms are the crystallization that a nation undergoes a lot and finally accumulated. it has a strong nation color and distinctive cultural connotation. Thus unique meanings of language come into being.