Abstract: Collaborative governance of ecological environment in cross-border watersheds still faces the problems of incomplete horizontal governance evaluation system and low willingness of governance entities to actively implement policies.The dynamic mechanism of collaborative decision-making among governance entities can be explored from the perspective of improving the vulnerability of the ecological environment in watersheds and realizing ecological value.We constructed the Nash non-cooperative game, Stackelberg master-slave game, and collaborative cooperative game models to analyze the ecological environment collaborative governance strategies of upstream and downstream governments in the watershed, and established a horizontal ecological compensation mechanism based on changes in the vulnerability of the watershed ecological environment.Research finds that the efforts of upstream and downstream governments are insufficient under non-collaborative cooperation.Collaborative cooperation is more conducive to improving the ecological environment at the economic level than non-collaborative cooperation.It is difficult for upstream and downstream governments to spontaneously achieve collaborative cooperation.Through a horizontal ecological compensation mechanism, it can effectively promote cooperation between upstream and downstream and improve the efficiency of cross-border watershed ecological environment cooperation and governance.The research results can provide references for the construction of intergovernmental cooperation mechanisms in cross-border river basins and the formulation of horizontal ecological compensation policies.