The paper shows that characteristic, trend and driving forces of quantity change of cultivated land and the disciplinarian of balance between supply and require for cultivated land under food supplies safety long-term in the developed region by the analyses of relation between change of cultivated land and humanity factors near 20 years in Jiangsu. The results indicates that descending rate of cultivated land in the developed province is more eighteen percent than the mean value of whole country, that extent of cultivated land use change presented diversity like terraced or radiation state which is becoming diminutive from the much more developed region to the general developed region, and that driving forces of cultivated land change are economy increase, society progress, the advancement of science and technology, security of food, policy, market, and the safety of environment etc. The descending trend of cultivated land in quantity endanger the balance between supply and demand and the security of food within the period of too many population, therefore we should take effective measures to prevent it as fellow: the protection of farmland, the construction of land-use system and the ownership of land in the country, the avoidance of police' misdirection, saving on land-use, the protective development and study on land resource in supporting, and the fallow of cultivated land in the regulation of agricultural structure.