Improve agricultural support policies, consolidate the agricultural foundation, and consolidate and enhance food productivity is the latest food security development strategy proposed by the Central No. 1 Document in 2019. Based on the panel data of 23 provinces from 2007 to 2017, this paper constructs a dynamic panel GMM model to study the impact of agricultural policy support on grain productivity in wheat, rice and corn producing areas.The results show that the current agricultural policy support has a significant incentive effect on China's grain productivity. The fiscal support policy affects productivity by affecting wheat, rice, corn planting area and yield, and fixed asset investment increases productivity by increasing wheat and rice yields. The industrial structure reduces productivity by reducing the area planted with wheat, rice and corn. Food prices have little impact on the three grain productivity, and agricultural insurance policies, resilience, fertilizer use, and mechanization have positive effects on China's grain productivity. Finally, some suggestions were put forward, such as adjusting the direction of financial investment in agriculture, strengthening the basic investment in agriculture, optimizing the regional layout and factor input, implementing differentiated grain prices and subsidy standards for agricultural modernization technology.