Abstract: In order to explore the grain-size distribution characteristics and geo-genetic types of land desertification in Mo Us desert, the research on the grain-size characteristics of sediments since late Pleistocene has been carried out in the desert area and neighboring area such as inside desert, sand co-vered loess plateau, loess plateau and river valley.The research result shows that sediments of different geologic genetic types are the fundamental material source of sandy desertification in these areas and the distinguishing of different types of the sediments is the theoretical basis of classification of different geo-genetic type of sandy desertification.The contribution of different geological roles on the land desertification and its significance to prevent and deal with the land desertification have also discussed. It is believed that the land desertification in Mo Us desert area is charactrized by the in-situ sand source and the hydraulic carriage by surface flow is the important way to transport the sand. Modern sandy desertification in Mo Us desert and its neighboring regions is a further process of transition, sorting and sedimentation by wind with more intricate grain size distribution characteristics.

Key words: Mo Us desert, sediment, grain size characteristics, sandy desertification