Abstract: the Hexi region lies in the arid and semiarid regions of China, its fragile ecological environment and severity desertification were caused by natural environments change and humanity influences. With the development of remote sensing and GIS, it provides an effective method to research desertification. In this paper, MODIS data between June and August in 2002 and 2008 were used to analyze desertification, and five indexes {including MSAVI (Modified Soil-Adjusted Vegetation Index), Surface Albedo, LST (Land surface temperature), FAVI and TVDI} were used to assess degrees of desertification. The results indicate that the desertification land in Hexi region is larger and occupies more than 50% land in total land. The desertification land was decreased by 6431.64 km2 in 2008, the non-desertification land and slight desertification land increased by 2.25 and 0.26%, respectively; moderate, severer and extremely severer desertification land decreased 1.4, 1.09 and 0.31%, respectively. Summery, the reverse rate of land desertification is larger than development rate, and shows that reversing is common tendency but part region is in desertification development. In the study region, it mainly is slight desertification land, 23.64 and 23.90% in 2002 and 2008, respectively, and then belongs to moderate, severer and extremely severer desertification lands.

Key words: Hexi region, desertification, trend, RS and GIS