Ecological technology innovation with environmental benefits as the core has become an inevitable choice for water environment treatment PPP projects (WETP-PPP), and government supervision and public participation are essential driving factors for eco-technological innovation. To explore the influence of public participation on the behavior of the government and private sector in the WETP-PPP, this study constructed an asymmetric evolutionary game model of government supervision and private sector ecological technology innovation behavior under public participation. The main contribution of this study is to explore the mutual evolutionary regularity of the private sector and government supervision department and the influence of public participation level on public and private behavior in different scenarios. The results showed that the government can reduce the supervision cost by increasing the public’s active participation and improving environmental regulation measures to achieve a win-win situation of economic and environmental performance.