According to primary performance status of public policy implementation in China, this paper researches performance evaluation from two aspects (positive and negative) in macroscopic environment. System dynamics method is adopted to explain the mechanism of these two kinds of effects on our public policy implementation. By computer simulation, the core execution of public policy has constructed the “local government performance evaluation of public policy implementation in the stock and flow model of the overall system dynamics”, and investigates mechanism of performance evaluation of public policy implementation in our local government, in order to reach a more standardized and improved system of public policy.