Public private partnership(PPP)projects have a long operation period, which is prone to regulatory capture and weaken the regulatory function of the government. Based on the premise that the government is inferior, an independent third-party supervision agency is introduced to supervise the water ecological PPP project, and a game model is constructed to analyze the impact of the governments reward and punishment strategies on the behavior of the players from the perspective of evolutionary game. The simulation results show that the short-term negative impact of regulators on government punishment is very significant, but the long-term impact is small. At the same time, the simulation results find the scope of government rewards, and also find out the relationship between the cost of third-party regulators and their regulatory performance.