Abstract: Food security is the “ballast stone” for sustained and stable economic and social development. Compared with the developed countries in Europe and America, the farmland resources in East Asian countries are scarce, and the grain self-sufficiency rate is not dominant, so it is difficult to achieve stable and increased grain production only by increasing grain yield per unit area. Under the background of rising global food supply risk, it is an inevitable choice for East Asian countries to curb the “non-grainization” problem of farmland. Looking at the adjustment trend of planting structure in representative countries in East Asia, the “non-grainization” problem of farmland has become more and more serious in Japan and South Korea due to the long-term implementation of rice production restriction and price protection policy, while China has realized the structural transformation from “non-grainization” to “grainization” by combining administrative constraints and incentives. It should be noted that there are a series of internal driving factors for the “non-grainization” problem of farmland under East Asian agricultural mode, including the change of farmers’ planting preference caused by the non-agricultural transfer of labor force, the investment incentive effect caused by the improvement of land ownership stability, and the “involution” of farmland circulation that hinders the improvement of scale benefits. To handle this problem properly, it is necessary to improve the guarantee mechanism of farmers’ income from grain production, so that the policy goal of stabilizing grain planting area can be smoothly transformed into farmers’ voluntary actions.