The reform of grain price floor policy is an important part of the structural reform of agricultural supply side. The grain price floor policy has played an important role in increasing farmers’ income and ensuring grain production growth. However, some negative impacts including the imbalance of grain supply and demand structure became increasingly prominent. On the basis of reviewing the historical evolution stage of the grain price floor policy, this article analyzed the adverse impacts of the price floor policy on the supply side and examined the structure and quality of grain supply and the problems faced by the grain price floor policy under the background of agricultural supply side reform from seven aspects such as the lack of farmers’ decision-making basis among others. This paper suggests to transform the goal of the grain price floor policy, to build a reasonable subsidy mechanism, to cultivate diversified market entities, to enhance the guiding role of the price floor policy based on ensuring the return of cost or lower profit, to adjust the reserve structure to stimulate market vitality, and to establish a linkage mechanism of “futures plus insurance”.