Abstract: Purpose/Significance The smooth implementation of PPP projects requires a win-win cooperation between the government and social capital. The credibility of local governments plays a significant role in promoting the smooth implementation of PPP projects. At the same time, the role of public participation must be fully considered. Design/Methodology In this paper, under the condition of the limited rationality of the three parties (local government, social capital and the public), the costs and benefits of the three parties under different strategic combinations are analyzed, and the tripartite cooperative evolutionary game model is constructed. Through the analysis of the tripartite evolutionary game, the stability strategies of each participant under different states are obtained. Conclusions/Findings The analysis results show that the punishment coefficient of the superior government department to the local government has a sudden point, which can restrain its behavior to a certain extent and make it pay more attention to public credibility and keep its promise. The promotion of public participation has a positive impact on social capital under certain conditions, which can curb the opportunistic behavior of social capital and influence the strategic choice of local governments. The reward income obtained by the public has a certain influence on the tripartite cooperation.