Taking the introduction and implementation of agricultural producer services policies in some of 163 cities in major grain producing areas as a quasi-natural experiment. By using a DID(Difference in Difference) method to identify the impact of the causal effect, heterogeneity and influence mechanism of agricultural producer services policy on agricultural development in major grain producing areas.The research results were as follows. Firstly, policies not only effectively promoted agricultural development, but also optimized regional industrial structure, and the results passed the parallel trend test, placebo test and the robustness test of lagging one period of dependent variables. Secondly，the heterogeneity of policy effect was significant, the policy effect of agricultural development in mountainous areas was stronger than that in non-mountainous areas, the policy effect on new agricultural management entities wasstronger than that on smallholders, and the policy effect decreased continuously with the improvement of agricultural development level, showing the characteristics of "benefit the poor but not the rich". In addition, the policy released the policy dividend mainly through the mechanisms such as promoting production trusteeship, cultivating service organizations and introducing modern factors of production, so as to achieve the goal of promoting agricultural development.