This paper uses the location quotient index and relative growth rate to measure the comparative advantage in the production of rice, wheat, corn and soybeans in different provinces of China. The result shows that there exists great difference in the production of major grain varieties in different areas of China and that the northern areas are accumulating their competence. Because great changes have taken place in the space structure of the production of major grain varieties and water resources will constitute a rigid restraint in the production of grain, it will become the priorities in guaranteeing the Chinese future food safety to promote the nurturing of areas with advantage in the production of corn and soybeans, and it will become the key for guaranteeing the balance between the demand and supply of grain to enhance the development of grain circulation system.