Abstract: The object of study is Wuqi County, which is biggest area of the conversion of cropland to forest or grassland of China. Analyzed the character of cropland changing and grain security from 1997 to 2006. Basing on all of these study, using minimum cropland average per capita and cropland pressure index model as a means to analyze 10 years’ changing characteristic of this two variant . Therefore, the paper puts forward some countermeasures and suggestions to ensure cropland dynamic stable and the grain security.