Imagining positive contact with outgroup members can improve intergroup attitudes and promote more positive intergroup relations. In the society, the implicit gender prejudice still exists among the opposite sex, which will lead to individual's unwillingness to have social contact with the opposite sex, even produce antagonistic reactions, and reduce or inhibit the communication and cooperation between the opposite sex. Many studies proved that imagined positive contact can improve the cooperation intention with outgroup members, but the future behavior intention of individuals may not be transformed into positive intergroup behavior. Therefore, this study conducted two experiments to explore the influence and mechanism of imagined intergroup contact on implicit gender prejudice and cooperative behavior by Single Category Implicit Association Test (SC-IAT) and three cooperation paradigms. Experiment 1 examined the effect of imagined intergroup contact on implicit gender prejudice. Participants were 161 undergraduates (79 boys and 82 girls). Experiment 1 was conducted with a 2 (imagined contact: imagined positive contact, neutral imagined scene) × 2 (gender: male, female) between-subjects design. Participants were asked to finish the questionnaire of prior contact experience, imagine positive contact (experimental condition) or unrelated situations (control condition), and complete the task of SC-IAT. The results show that: (1) Imagined positive contact can significantly reduce the implicit gender prejudice of the opposite sex ( F(1, 156)=11.23, p<.01, η2=.07 ); (2) There is no significant gender difference in the implicit gender prejudice of the opposite sex. These findings suggest that imagined intergroup contact can effectively reduce the implicit prejudice by arousing individual's positive emotional experience. Experiment 2 examined the effect of imagined intergroup contact on cooperative behavior and the mediating role of implicit gender prejudice. Participants were 100 undergraduates (37 boys and 63 girls). Experiment 2 was conducted with a 2 (imagined contact: imagined positive contact, neutral imagined scene) × 2 (gender: male, female) between-subjects design. The previous process was the same as Experiment 1. Finally, participants were asked to complete three cooperation paradigms, namely prisoner's dilemma, public resources dilemma and public goods dilemma. The results show that: (1) In the prisoner's dilemma, imagined positive contact can significantly increase the cooperative behavior between the opposite sex ( F(1, 95)=10.13, p<.01, η2=.10 ), and implicit gender prejudice plays a partial mediating role ( 95%CI [.004, .062] ); (2) In the public resource dilemma, imagined positive contact only reduces the cooperative behavior of boys ( M positive contact -M control condition =12.29, p<.05 ); (3) In the public goods dilemma, there was no significant effect of imagined intergroup contact on the cooperative behavior. These findings suggest that imagined intergroup contact has different effects on intergroup cooperation in different social situations. These results support that imagined positive intergroup contact can not only change the intergroup attitudes, but also affect the cooperative behavior in the process of real contact.