Abstract: Two systems of indices for different levels of food security early warning are respectively designed. By means of the Spatial Decision Supporting System of Grain Supply and Demand Balance developed by authors，the situations of food security in whole country and different provinces are calculated and analyzed in recent years. The results showed that the two systems of indices can objectively and respectively reflect China's food supply and demand, can act as part of models of the Spatial Decision Supporting System of Grain Supply and Demand Balance. At the same time, the results of crop monitoring by remote sensing can become datum sources for the whole country's food security early warning, but at the level of province, it should be effectively integrated with statistical data.