Through analysis of total area of cultivated lands,change in internal structure and regional difference, we discussed the driving mechanism of cultivated land change in the Tsinghai Lake region.Results show that cultivated lands in the region exhibit an evolutionary tendency of steady increase,sharp increase,screw-type increase and sharp decrease.For the internal structure,area of irrigable land has increased greatly,and areas of both nearby mountains and tope mountains have a relatively declined tendency.Areas of irrigable land and other types of cultivated lands change alternately.Regional difference of cultivated lands is characterized by a tendency of increase, non-synchronized change and then decrease in the area for the entire region.Besides natural factors,the major national policies and the agricultural policies are responsible for the changes in cultivated lands of the region.