Based on a geological map with measuring scale of 1∶ 500 000,the Qaidam Basin was digitized using MapGIS. According to the satellite images of Google Earth and topographic map of Google Maps as well as the field investigation,in this paper the distribution of modern sand desert in the Qaidam Basin was delimited. The aeolian accumulative formations of Holocene and Late Pleistocene were extracted from the digital geological map of the basin based on the available literatures,and then the maps of distribution of the desert during the Holocene Megathermal Period and the Last Glacial Maximum were sketched out. According to the distribution maps of the desert,the scope of the desert during the Holocene Megathermal Period contracted and was smaller than that of the modern one in the basin,and the desert responded well to the warm-humid climate. While the scope of the desert during the Last Glacial Maximum expanded rapidly and was larger than that of the modern one in the basin,and the desert responded well to the dry-cold climate.