Abstract: The existing literature rarely focuses on the agricultural economic growth effect and agricultural environmental effect of food price support policies. Different from the previous single-dimensional research, this paper incorporates food price support policies, agricultural economic growth and agricultural environmental pollution into an analytical framework,using the heterogeneous timing DID model and the mediating effect model to tested empirically the causal relationship and mechanism between grain price support policies and agricultural green growth.The study found that:The grain price support policy inhibits the green growth of agriculture, and this conclusion has strong robustness. The grain price support policy can reduce the non-point source pollution of agricultural fertilizer per unit area and slow down the agricultural output value per unit area through the two-day path of crop planting structure adjustment and agricultural labor transfer, which finally leads to the negative impact of the policy on agricultural green growth.Further analysis shows that under the current agricultural production mode, grain price support policy is difficult to achieve the combination of agricultural 'growth' and 'green'.The conclusions of this paper will further grasp the impact of grain price support policies and promote the green increase of agriculture.

Key words: grain price support policy, agricultural green growth, heterogeneous timing DID, mediating effect