In order to clarify the spatial differentiation of cultivated land planting structure and its influencing factors at the micro-geographical scale, the typical grain-producing counties in Heilongjiang Province were selected as the research area, the 1km2 geographic grid was used as the research unit, and the regional statistical method, spatial association analysis method and geographic detector model were used to analyze the spatial differentiation characteristics of the three main crops of rice, corn and soybean, and reveal the influence mechanism of the spatial differentiation of regional cultivated land planting structure. The results showed that the planting structure in the region was mainly single soybean type, single corn type and corn-soybean type, and single rice type and soybean-corn-rice type were the secondary types. There were some differences in the spatial agglomeration characteristics of different crop planting structures. Rice was mainly HH type, and corn and soybean were mainly HH and LL types. Terrain were the dominant factor in the spatial differentiation of rice planting structures, and that of corn and soybean were climatic and soil conditions. Natural conditions were still the key influencing factors in the spatial differentiation of cultivated land planting structures. The spatial differentiation of cultivated land planting structure was the result of multi-factor interaction. The interaction of market location and traffic location with other factors greatly improved the spatial differentiation of corn planting structure. For rice, irrigation potential had the strongest impact on factor interaction. However, the effect of factor interaction on the spatial differentiation of soybean planting structure was not much improved. The research results were helpful to understand the formation mechanism and differences of the spatial differentiation of different food crops, and provide a scientific basis for the optimization and adjustment of cultivated land planting structure.