This study was based on dynamic measurement of deserted land in Chaidamu Basin,Qinghai Province,from 1959 to 2004.Results showed that the area of deserted land in the basin increased from 5800000hm² in 1959 to 10254000hm² in 1994,with an increased percentage of 2.13% per year on average.With the implementation of forest policies,the area of deserted land in the basin descended from 10254000hm² in 1994 to 9495000hm² in 2004,with a yearly-dropping percentage of 0.67%.The trend of desertification is still aggravated in some regions.The main factors for the expansion of deserted land were studied as well.Finally,some prevention countermeasures were proposed on the basis of the above study and analysis.