Abstract: Grain security is a condition related to the ongoing availability of food,which is the important component of the national security. Consolidating the basic position of agriculture and ensuring food security has become a common concern of the government and the academic community under the new economic normality in China. Using the coefficient of grain production variation,the coefficient of variation and the spatial analysis method, the paper studied spatial-temporal evolution of grain production and current situation of grain security in China.We can get the following conclusions: (1)From 2000 to 2003,due to the rapid urbanization and industrialization which led to the sharply occupation of high quality farmland and the migration of a large number of young workforce from countryside to city,the sowing areas decreased,total grain production declined with fluctuation. (2)From 2004 to 2015,the Chinese government had implemented a series of policies,such as food subsidies,agricultural tax relief,the protection of basic farmland and arable land,which promoted the continuous growth of grain production for the twelve consecutive years. (3)As to different grain crops,corn production had increased substantially from 9 681.9×10⁴ t in 1990 to 22 463.2×10⁴ t in 2015,while the production of rice and wheat showed a slight growth trend. In addition,this paper analyzed the regional distribution of grain production. The gravity of grain production showed deviation,shifted from southwest to northeast during 2000-2015. As to the contribution rate of grain production in different regions to the total grain production of China,southern coastal areas showed the biggest decrease rate -5.02%;On the other side,the northeast region had the highest contribution rate increase,which was 7.75%,and the contribution rate in Mongolia and Xinjiang Uygur Autonomous Region increased 2.61%. The concentration of rice production was further improved,mainly concentrated in the middle and lower reaches of the Yangtze River and northeast China,and the wheat production was concentrated in the Huang-Huai-Hai Region and the middle and lower reaches of the Yangtze river,corn production was mainly distributed in northeast China. The area coverage of grain yield security had been increasing,the number of provinces where food yield is sufficient increased from 11 to 16,with more than 400 kg grain production per capita. In the future,grain security is not just concerned with yield security,food structure safety,food safety and ecological environment safety caused by grain production should be paid more and more attention to in all directions and at many levels.

Key words: grain yield, grain security, temporal and spatial evolution, China