Abstract: Desertification is one of the most serious problems in the world,which deeply damaged the social-economy and the environment.Desertification in Yanchi County of Ningxia Hui Autonomous Region is notable.Based on TM images in three periods(1986,1996,2000),and land-use map,relief map and other information of Yanchi County,three desertification maps and two dynamic maps are made through the GIS software,ARC/INFO.Supplied by the GIS and database analysis methods,the structure change and the developmental characteristics of desertification in Yanchi are described in detail.Under the limitation of the other non-desertification lands,the area of desertification in Yanchi became smaller during 1990s,but the grade became higher.The major desertification reasons are unreasonable agricultural practices,heavy livestock grazing and firewood cutting,and the construction of industry and transportation.

Key words: desertification, remote sensing, GIS