Abstract:Nowadays, the contradiction between economic development and environmental resources is becoming more and more acute.In the sewage treatment PPP model, there are a series of problems such as imperfect law, government function is not clear, lack of investment and so on.PPP model is a new way to finance public infrastructure financing,and it is helpful to reduce the risk of project financing.In this paper, by using the optimization of the Potter diamond model combined with analytic hierarchy process and TOPSIS method, using the theory and empirical, qualitative and quantitative methods to analyze the problems faced in PPP model,At last putting forward the suggestions of perfection of laws and the transformation of government functions, increasing investment, improving enterprise competitiveness will be conducive to promoting the sewage treatment for the development of PPP model.