Abstract: In the paper, a new tripartite evolutionary game model analyzing collaborative governance path of cross regional pollution in Urban Agglomeration is constructed based on decentralized environmental regulation. In order to solve environmental problems under aggregate development, cooperative parameters of local government, including governance cost, opportunity cost and governance income, and policy parameters of the central government such as economic incentives and subsidies are mainly considered. Moreover, the strategy selection of different subjects is studied which discusses the influencing factors and interaction relationship. And the equilibrium stability strategy of the system with existence conditions is determined. At last, the evolution process of different strategy combinations is simulated. Then some suggestions are put forward to establish incentive and restraint mechanism, joint prevention and control mechanism, and regional integration and coordination mechanism. The results are shown below. For local governments, the probability of choosing cooperative behavior will increase with the probability of other local governments choosing cooperative behavior and the probability of central government choosing strict supervision. While the probability of central government choosing strict supervision will increase with the decrease of the probability of local government choosing cooperative behavior. The evolution speed of system stability strategy is affected by the proportion of its own and other agents’ strategy selection. No matter how the proportion value changes, the final strategy decision of the group will not be changed.