Abstract: Take for example land desertification in the desert-loess zone on the southeastern margin of the Mu Us desert, the land desertifications in the study area are divided into the sands interior in-situ sand accumulation type, river valley in-situ sand accumulation type, weathering-residual in-situ sand accumulation type and windblown type. The grain-size features of desertified lands of different genetic types and their geological implications are analyzed intensively. In addition, the regional distribution of different types of land desertification is analyzed by means of remote sensing interpretation and geological reconnaissance. At last, the theoretical and environmental-geological aspects of the classification of land desertificatiom of different geological origins and their great significance for the prevention and control of land desertification are discussed and countermeasures and suggestions for the prevention and control of land desertifications of different origins are put forward.