Abstract: From the perspectives of the demand and supply， the research studied the influence factors of Chinas grain security with the method of systematical analysis. The results indicated that grain sowing area， damage area， effective irrigation area， cultivated area and the total power of agricultural machinery were the key factors that influenced the coefficient of grain security of China; the basic role of effective irrigation area and grain sowing area in guarantying national food security had been weaken; while the effects of total power of agricultural machinery， price fluctuation of agricultural means of production and urbanization rate on grain security had been constantly strengthened. However， the natural disasters will bring negative effects on grain security both in long-term and short-term.

Key words: grain security, grey slope coefficient correlation degree, grain supply and demand