Abstract: Under the two situations of the global unprecedented changes in a century and the overall strategy of the great rejuvenation of China, the domestic grain support and protection policy is facing new requirements and challenges. Since the country started a new round of minimum purchase price policy reform in 2015, the impacts of continuous policy adjustment on rice production and grain security deserve attention. Based on the national and provincial panel data from 2004 to 2019 and applying the generalized synthetic control method, this paper analyzed the mechanism and the impacts of the new round of minimum purchase price policy adjustment on acreage, per unit yield and total production of rice. Results show that the new round of policy adjustment has a significant negative impact on the sown area of rice with obvious regional heterogeneity, which brings the fluctuation of rice yield. Further analysis found that under the pressure that the minimum purchase price is no longer continuously raised, the sown area of paddy rice has been significantly reduced, and the increase in output mainly depends on the advance in yield per unit. Therefore, this paper provides the following suggestions: paying attention to the impacts and risks of this round policy adjustment, maintaining the stability of the basic framework of the domestic minimum purchase price policy, adhering to the main principle of stepby-step and the direction of market adjustment, further deepening policy reform, improving supporting policies, and strengthening biological breeding and technological innovation to firmly hold the bottom line of national grain security.