Abstract:As the most basic agricultural production data, seed plays a very important role in grain production in China. However, the domestic scholars have not studied the seed input as an important variable in the study of the substitution of grain input factors. Therefore, in this paper, grain production model is constructed with seed input as one of the important variables. The output elasticity, marginal product and substitution elasticity of input factors are measured, and the substitution of factors is studied. The research results show that seed input has a certain substitution effect on the labor force, but the substitution effect on the labor force is mainly agricultural power, while seed input mainly plays a role in increasing grain production. According to the results of the study, the input of modern agricultural production factors such as agricultural machinery and seeds plays a very important role in grain production. In order to ensure the stable growth of grain production, we should improve the technical level of variety improvement and give full play to the role of seed input in increasing grain production. We should increase the support of agricultural machinery subsidy policy, encourage farmers to buy agricultural machinery and put it into production, and give full play to the substitution role of agricultural machinery.