The essentialist theory of ethnicity contends that ethnicity is determined by nonmalleable, deep-seated essence and the essence would give rise to stable personality traits and abilities across situations. On the other hand, the social constructivist theory denies the real existence of ethnic essence; it contends that ethnicity is arbitrarily created due to social and political reasons in historical contexts. Most western studies have shown that the psychological essentialism about gender, race, homosexuality, and mental illness causes negative intergroup relationship. Although Gao & Wan(2013) found that essentialist theory of ethnicity affected people’s intergroup identity and caused negative ethnic stereotype, it was unknown the relationship between essentialist theory of ethnicity and cross-ethnic interaction. To examine the effect of psychological essentialism of ethnicity on cross-ethnic interaction, the authors conducted 2 studies with the Tibetan college students in China. First, 113 Tibetan college students from two colleges participated in Study 1. They completed questionnaires aimed at assessing their psychological essentialism of ethnicity (the Chinese version, No et al., 2008), out-group contact quantity and quality (Islam & Hewstone, 1993), and social distance (Bogardus, 1925). The results were as following: (1) Correlational analysis showed that psychological essentialism of ethnicity negatively correlated with contact quantity(r = -0.24, p<.05) and quality(r = -0.32, p<.001), and positively correlated with social distance(r = 0.51, p<.001); (2)Hierarchical regression analysis revealed that, after statistically controlling for the effects of school type and socially desirable responding, psychological essentialism of ethnicity separately explained 2.9%, 9.6%，25.4% of variance for contact quantity, contact quality and social distance. Second, 74 Tibetan students participated in study 2. An experimental method was used to test the effect of psychological essentialism of ethnicity on Tibetan students’ cross-ethnic interaction willingness. This study was a 2 (priming condition：psychological essentialism vs. social constructivism)× 2(target of cross-ethnic interaction：Han vs. other ethnic interaction)mixed design. The priming condition was a between-subject variable, cross-ethnic interaction willingness of different target was a within-subject variable. Participants were randomly assigned to read the article advocating the essentialist view of ethnicity or the article advocating the social constructivist view of ethnicity. The results showed that participants in the social constructivism condition displayed a strong willingness of interaction between Tibetan-Han(M = 4.41, SD =0.64 ) than those in the psychological essentialism condition(M = 3.97, SD = 0.83, F (1，61) =13.0，p<.001，η2=.18 )when socially desirable responding was a covariate. The study suggests that psychological essentialism of ethnicity is the important influencing cross-ethnic interaction factor. Practical implications of these results imply there are two ways to improve ethnic relation in China. First, lay people’s theory of ethnicity can be used as a vehicle for improving ethnic relations. Specifically, we can teach people to hold more social constructivist belief and less essentialist belief of ethnicity, thereby weakening the psychological boundary among different ethnic group. Second, we can provide more contact chances by creating multi-ethnic mixed schools or classes to promote cross-ethnic interaction.