Abstract: Previous research shows that ethnic essentialism has negative influence on many aspects for interpersonal and intergroup relationship—such as ethnic essentialism would increases the cognition of intergroup differences, individuals who hold strong ethnic essentialism beliefs has more vehement stereotypes and prejudices towards other ethnic groups, and ethnic essentialism also hinder the cross-ethnic interaction and cultural adaptation, meanwhile ethnic essentialism is "the legal reason" that mainstream groups maintain unequal social status, etc.. Therefore, the current study only examines the negative influence of ethnic essentialism on interpersonal and intergroup relationship, has not yet explored whether ethnic essentialism can change. Supposed it can be changed, which factors can be used to change the mechanism? According to perspective from intergroup contact theory, this study examines the mechanism of weakening ethnic essentialism beliefs from an intergroup contact theory perspective. Study 1 selected 670 ethnic minority and mainstream groups of college students in China as subjects, using the questionnaire method to investigate three core variables—include ethnic contact, ethnic essentialism and contact attitude—and the relationship between among 3 variables would be analyzed. Results of this study show that for minority subjects, there is a significant negative correlation between ethnic contact and ethnic essentialism, for mainstream group subjects, although there is negative correlation but without significance; and there is a significant positive correlation between ethnic contact and ethnic contact attitude. Study 2 selected 241 minority college students as subjects to investigate four variables —ethnic essentialism, cultural identity, cultural similarity perception and ethnic contact (with majority group), and to examine the mediating role of cultural identity and cultural similarities between ethnic contact and ethnic essentialism. The result shows that culture similarity is positively correlated ethnic contact, while cultural identity and ethnic contact showed a significant negative correlation; cultural identity and cultural similarity plays a mediating role between ethnic contact and ethnic essentialism. In conclusion, it can be analyzed from this research results, the author argue that ethnic contact can weaken ethnic essentialism, promote interaction among the ethnic groups and improve ethnic relations. the mechanism that ethnic contact weakens ethnic essentialism is that it strengthens cultural similarity perception between ethnic groups and decreases ingroup cultural identity. Therefore, in the practice of promoting ethnic relations, it is necessary to create opportunities for contact and communication among ethnic groups to reduce prejudice by weakening ethnic essentialism, which can promote positive ethnic relationship. This research enriches the conclusion on psychological mechanism of intergroup contact improving intergroup relations, and deepen the understanding about ethnic essentialism, which also contribute to relevant theory and practice.