This paper,helped by Excel software and based on the analysis of dynamic fluctuation of cropland,population and grain output since Henan Province opened to the outside world,analyzes variant characteristics of minimum cropland acreage per capita and pressure index on cropland.

By using regression analysis and prognostic theory,the minimum cropland acreage per capita,and cropland pressure index model were analyzed with the consideration of changes in cropland,population and grain output since enforcement of the reforming policy.

Change of per capita grain and per capita cultivated land in Shaanxi province;

Based on the sense analyzing the situation of grain supply and the trends of cultivated land resources, they are indicated that the increase of per capita grain has slowing-down and the decrease of per capita cultivated land has been speeding within last decade years in Shaanxi Province.

The concepts of minimum per capita cultivated area required,index of growing area size pressure and labor carrying capacity of land resources are put forward,and the amounts of surplus labor are computed for various counties.

The thinking,method and procedure for calculating the security line of the per capita cultivated land are expounded and the security lines for Jining city are calculated.