TM data from 1986 to 2000 covering Shaanxi Province,Gansu Province,Ningxia Hui Autonomous Region,Qinghai Province,Xinjiang Wei Autonomous Region and western Inner Mongolia Autonomous Region were digitally interpreted to determine land use/cover modification.Remote sensing image processing software and Geographic Information System software were used in the research.Analysis methods included image enhancement,pseudo color composite,geometric rectification,mosaic and subset,and graphic database and attribute database establishment.The TM interpretation results for each county in the six regions were added.Three classification levels were adopted for land use/land cover.At the first level six classes were used including cultivated field,forest,grassland,water body,urban and unused land.In 1986,the area of desert,sand field and desertified land across the six regions was 85425467hm²( 26% of the total area),which was found mostly in Xinjiang,western Inner Mongolia,Qinghai and Gansu.Xinjiang was most severly affected,with 52035232hm²( 32% of the region) affected.In 2000,the area of newly desertified land across the six regions had increased by 1610062hm² and redesertified land covered 291776hm², resulting in a net increase of 1318286hm²(0.4% of the total region).Of the six land cover classes,grassland was most severly affected(797081hm²)comprising 50% of the newly desertified land.