Abstract The improvement of intergroup relationship by common ingroup identity model has been supported by several studies, however, those studies take the reduction of intergroup bias as the main indicator of intergroup relationship improvement. Although eliminating negative intergroup attitudes is an important way to improve intergroup relations, fostering or promoting positive intergroup attitudes is equally important. It’s known that psychological compatibility is an important manifestation of intergroup harmony. Therefore, the current study focuses on the promoting effect of common ingroup identity on psychological compatibility. Two experiments were conducted to explore whether common ingroup identity can promote psychological compatibility and its psychological mechanism. Experiment 1 recruited college students(N=102) who were randomly divided into 3-person groups. We manipulated common ingroup identity by re-categorization and measured explicit psychological compatibility (the psychological distance and feeling thermometer as the two indicators). The results showed that common ingroup identity within the group psychological distance was significantly closer to that of the separate group, and the feeling temperature of the outgroup of common ingroup identity was significantly higher than that of the separate group; A total number of 84 ethnic minorities college students took part in experiment 2 which took 2 (group categorization: common ingroup vs. separate group) x 2 (ethnic: Bourau vs. Hmong) between-participants designs. This experiment further verified the common ingroup identity for the promotion of psychological compatibility effect, and explored the relationship between the mechanism. The results showed that: (1) On explicit psychological compatibility, there was a main effect for group categorization. The psychological distance of the common ingroup identification group was significantly closer to that of the separate group, and the feeling temperature of the outgroup in the common ingroup identification group was significantly higher than that of the separate group; (2) On implicit psychological compatibility (GNAT), the main effect of group categorization was significant. The Sensitivity index of the common ingroup identification group was significantly higher than that of the separate group, the response of the subjects in the group with common ingroup identity to “non- ethnic + self-words” was significantly lower than that of the separate group; (3) With perceive similarities as mediating variables, group categorization as independent variables, as well as the explicit psychological compatibility and implicit psychological compatibility as the dependent variable respectively, the mediating effect was tested by the Bootstrap method. The results showed that the mediating effect of perceived similarity was significant. Two experiments proved that common ingroup identity can promote psychological compatibility at both explicit and implicit levels measurement, and its promoting effect was realized through perceived similarity. The present expands the Common Ingroup Identity Model from the explicit level to the implicit level. It provides evidences on the implicit level for the common ingroup identity to make the former outgroup closer to the self and shorten the intergroup psychological distance, which also confirms the validity of GNAT paradigm in the research of psychological compatibility.It's also found that the promotion of intergroup psychological compatibility by common ingroup identity is achieved through perceived similarity, this discovery provides an effective practical strategy for realistic social management.