This thesis is constructed in the following structure. Chapter One is the literature review. Firstly, it introduces the definitions of idioms, and then it reviews the previous studies on animal idioms. Only when the present research result has been attained，can the further study be carried on. From the past researches on idioms in the West and at home, readers will get a rough acquaintance of the study on the idioms. In the next chapter, the author makes a comparison of English and Chinese animal idioms from four perspectives. To help English learners use animal idioms correctly, the author introduces two translation methods: foreignization and domestication. After the systematic study on animal idioms, the readers will definitely have a scientific and specific understanding of them and have a better intercultural communication.

2. Literature Review

2.1 Definition of Idioms

2.1.1 Definitions of English Idioms

Many versions of definitions have been assigned to the terminology idiom. According to the commonly accepted one, idioms are linguistic expressions, consisting of two or more words，whose overall meaning cannot be predicted from the constituent parts (Kovecses 1996:326).

Oxford Advanced Learners’ Dictionary of Current English (1989:428) defines an idiom as: (1) language of a people or country; specific character of this, (2) (gram.) succession of words whose meaning is not obvious through knowledge of the inpidual meaning of the constituent words but must be learned as a whole. 

    According to Webster’s New World Dictionary of the American Language (1999：521), idiom means an accepted phrase, construction, or expression contrary to the usage patterns of the language or having a meaning different from the language or having a meaning different from the literal.”

From the above definitions of idioms we may draw the conclusion that an idiom is a fixed group of words or a single word, even a sentence, with a special meaning that cannot be guessed from its structure. English idioms include idiomatic phrases, proverbial sayings and a number of slang expressions．