摘要： The simple understanding of ethnicity by lay people is called the lay people’s theory of ethnicity, two theories are used to interpret the ethnicity by lay people in their everyday life. One of the theories contends that ethnicity is determined by nonmalleable, deep-seated essence and the essence would give rise to stable personality traits and abilities across situations, this is called the essentialist theory of ethnicity. The other theory, however, denies the real existence of ethnic essence, ethnicity is a social construction that is arbitrarily created due to social and political reasons in historical contexts, which is termed the social constructivist theory. Some western studies have shown that people have different interpretation about ethnicity cause different group perceptions and group relations. It is necessary to test and extend these results in another social background, like the Chinese one. First, 351 students from different ethnic groups participated in Study 1. They completed a questionnaire aimed at assessing their attitudes towards inter-group perception, ethnic identity, lay people’s theory of ethnicity, and out-group contact attitude. The results showed that: (1) the stronger essentialist belief a participant has, the more sensitive he or she is about group difference; (2) essentialist theory affects people’s inter-group identity, i.e. the deeper one believes in essentialism, the tenser he or she feels about in-group identity and bias, the more passive attitude is hold towards out-group contact. Second, 104 Han students participated in Study 2. An experimental method was used to test stereotyping differences against the minorities in relationship to lay people’s ethnic theories. Participants were randomly assigned to read the article advocating the essentialist view of ethnicity or the article advocating the social constructionist view of ethnicity. The result illustrates that: participants in the essentialist ethnicity condition showed stronger stereotyped impressions, especially negative stereotyping than did those in the social constructionist condition, but participants in the two conditions did not differ significantly on their positive stereotyping. In conclusion, the essentialist theory of ethnicity has a great influence on ethnic identity and ethnic stereotyping. Practical implications of these results imply that lay people’s theory of ethnicity can be used as a vehicle for reducing prejudice. Specifically, we can teach people to hold more social constructivist belief and less essentialist belief.