Abstract: The total area of farmland is decreasing at a rather high speed in recent years in China. The major reasons include: constructional land use, ecologic comeback, agricultural structure adjustment, catastrophic and so on, which will badly affect the food safety in China. By a new national plan, the insurance quantity of cultivated land should be 1.2108hm² by the year of 2010.The author analyzs that the number of farmland in China will decrease in short time based on the intrinsic model function,and advances several dynamic equations on arable land change, brings forward three projects based on numerical simulation . The result of the study shows: we must adopt the most severe measures, for the aim to nsure quantity of cultivated land of 1.2108hm². At last, the author presented three suggestions based on the numerical simulation results, which are to enhance the mprehensive plan of land use, to strengthen economical use of land, and to consolidate the management of land use.