Abstract: Mu Us Sandy Land is one major region of desertification development and reversion in Northern China. The natural factors for causing desertification had formed from the environmental variation during the Quaternary period. In the historical process, the desertification had been situated on the development or reversion in different period, resulted from change of land-use pattern (grassing or cropping) and human economic activities and natural conditions (rainfall). For last 50 years, the process of desertification had been much active due to the impact of natural factor and human economic activities. Based on the field in- vestigation and analysis of remote sensing data and GIS, we have monitored the desertified land in Mu Us Sandy Land. The results show that there were about 12 900 km² desertified land in earlier 1950s, 41 110 km² in middle of 1970s, 32 590 km² in late 1980 s and 30 650 km² in 1993. During 1950 to 1970, the desertified land had rapidly spread. Since late of 1980 the process of desertification has been in the reversion situation and there were about 9 460 km² desertified land have been restored for rangeland and farmland. The National Three-North Shelter Forest Construction and many efforts from the local government and people have contributed enormously for combating desertification in the region. It proves that man made desertification and only man can control it.

Key words: last 50 years, Mu Us Sandy Land, process of desertification, China