Changes in the political trust among Taiwanese students after visiting mainland China symbolize the effectiveness of the CPC’s political propaganda. This issue is critically related to the stability of Taiwan’s democratic polity and hence warrants the close attention of supporters of democracy from around the world. A total of 516 Taiwanese youth who visited mainland China on exchange programs were studied.  Four hypotheses were proposed by combining the theories of social contact, political socialization, and rational choice. The results show that after the students visited mainland China, the number of those with greater political trust in their home country was 13.46% higher than those with lower trust. The average change significantly increased by 0.06. All four hypotheses were supported by empirical evidence. After the cross-polity contact, students’ perceived hostility of the Communist Party of China was reduced, or they were more satisfied with the level of Taiwan’s democracy, or their evaluation of Taiwan’s industrial prospects were better, or they less willing to go to mainland China for career development, leading to greater trust in Taiwanese officials. This study makes a unique contribution to the literature by combining true-acquaintance contact and political mobilization to propose the perceived hostility hypothesis for changes in political trust.