The reform of corn purchase and storage policy is an important measure to support the market-oriented reform of grain price and assessing its effect on productivity is of great significance for the high-quality development of the corn industry. This paper studies the impact of the reform of corn purchase and storage policy on farmers’ corn productivity by adopting the Propensity Score Matching and Difference-in-Difference Model （PSM-DID） using the data of a large sample of farmers from fixed observation points across rural China during 2014-2019. The results are as follow. Firstly， the average effect of the reform of corn purchase and storage policy on the farmer’s corn productivity is 8.7%， and the results are still significant after a series of robustness tests such as substitution variables， change of samples， change of methods， placebo test and disturbance elimination policy. Secondly， the reform is divided into two stages： the cancellation of the temporary storage price and the implementation of producer subsidies. the implementation of producer subsidies has a greater positive impact on the productivity of corn than the cancellation of the temporary storage price. Thirdly， the results of heterogeneity analysis show that the positive effect is more pronounced for the reform of the farmer households with larger scale， higher level of specialization， higher degree of diversified work and lower corn productivity. Fourthly， the reform will increase the corn productivity of the farmer households by optimizing land resource allocation and increasing productive investment.