People use bilingual dictionaries whether language-teaching mythologists like it or not. Indeed, to many people the word "dictionary" means "a bilingual dictionary"(Hartmann 1983:45). In 1.1, we will concern learners’ preference for English-Chinese dictionaries. Equivalents are to the bilingual dictionaries as definitions are to the monolingual ones "The basic purpose of a bilingual dictionary is to coordinate with the lexical units of one language those lexical units of another language which are equivalents in their lexical meaning"(Zgusta 1971:294). In 1.2,we will make a survey of four English-Chinese dictionaries which are NECD, NAECD,ECD and its supplement and ANAD .These four dictionaries will be taken as examples to discuss their equivalents in the following chapters.Chapter II presents the defining process in English-Chinese dictionaries, which is the major part of the thesis. 2.1 concerns equivalents in English-Chinese dictionaries. Zgusta classifies equivalents into absolute equivalents, partial equivalents and no equivalents. Detailed discussion will be made on types of equivalents in entry words’ translation in 2.1.1 and two main equivalents, translational equivalents and explanatory equivalents will be concerned. The advantage of a translational equivalent over an explanatory one is that the former offers the users a lexical unit, which can be directly employed in the TL. We will compare these two types of equivalents in entry words’ translation. Then our focus will be put on five particular groups of lexical units, which are culture-bound words, scientific and technical terms, function words, encyclopedic words and new words. Culture-bound words cause particular problems of seeking equivalents in the compilation of bilingual dictionaries. When we discuss culture- bound words, first of all we have to mention the relationship between language and culture, which will be done in 2.2.1. The treatment of culture-bound words in English-Chinese dictionaries will be discussed in detail in 2.2.2 and five main methods of providing equivalents for culture-bound words will be mentioned. The five main methods are: 1) transliteration or transliteration plus explanatory notes in brackets; 2) transliteration with restrictive suffixes, if necessary with explanatory notes in brackets; 3) free translation or free translation plus explanatory notes in brackets; 4) literal translation or literal translation plus explanatory equivalents; and 5) explanatory translation. Besides these five main methods, there are some other methods, which will also be mentioned briefly, including providing pictorial illustration, culture notes and etymological information as further explanations or supplement equivalents for culture-bound words. Many scientific and technical terms have entered our daily life and how to treat them is a problem that bilingual lexicographers have to face.TThe treatment of scientific and technical terms in language dictionaries is different from that in subject dictionaries in two aspects: different defining contents and different defining ways. Three main ways of giving equivalents to scientific and technical terms in English-Chinese dictionaries will be discussed in 2.3.2 which are: 1) transliteration; 2) translating according to affix and free translation; and 3) free translation. 2.4 presents characteristics of function words and the treatment of function words in English-Chinese dictionaries. Whether encyclopedic words should be included or not depends on the purpose of the dictionary and the users’ demands. From Bejoint’s research, Hartmann’s investigation and Al-Kasimi’s criteria we know it is necessary to include encyclopedic words in dictionaries. Encyclopedic words in the thesis mainly refer to proper names.2.5 is devoted to concern the need of including encyclopedic words and the treatment of encyclopedic words. 2.5.2 is the major section of 2.5, which concerns the different treatment of encyclopedic words in English-Chinese dictionaries andEnglish-Chinese encyclopedic dictionaries first, t