The land use/land cover change of Xilin River Basin in the past two decades was investigated through land use/cover classification of four sets of Landsat TM/ETM images acquired on July 31, 1987, August 11, 1991, September 27, 1997 and May 23, 2000, respectively. Primarily, 15 sub-classes land cover types were recognized, including 9 grassland types at community level: F. Sibiricum steppe, S. baicalensis steppe, A. chinensis + forbs steppe, A. chinensis + bunchgrass steppe, A. chinensis + Ar. frigida steppe, S. grandis + A. chinensis steppe, S. grandis + bunchgrass steppe, S. krylavii steppe, Ar. frigida steppe and 6 non-grassland types: cropland, urban area, wetland, desertified land, saline-alkaline land,and waterbody. To make the time series land cover classification data applicable for land use/cover change quantification analysis, the cloud, waterbody and cloud shadow features were extracted from each of the raw land cover maps and overlaid as a subset map. Then the area corresponding to the subset in each land cover classification map was eliminated. After this procedure, each of the final land cover classification map of Xilin River Basin was optimized and ready for land use/ cover change detection. The main characteristics of land use/land cover change in Xilin River Basin over the past two decades were a significant decrease in area of meadow grassland, temperate grassland vs. significant increase in area of cropland, desert grassland, urban area and desertified land. From 1987 to 2000, the area of both F. sibiricum meadow steppe and S. bacalensis meadow steppe decreased steadily year by year, whose net decrease was 525.5 km2 and 201.5 km2. While the area of S. krylavii desert steppe and Ar. frigida desert steppe increased year by year, whose net increases were 1,282.7 km2 and 1,045.6 km2 respectively. The desert grassland had the greatest increase in area, i.e., 2,328 km2, equal to 56% of the total area of desert grassland in 1987. The cropland and urban area increased from 114.3 km2 and 25.2 km2 in 1987 to 332.1 km2 and 43.6 km2 in 2000, respectively. The A. lymus + bunchgrass steppe, A. lymus + forbs steppe had the greatest decrease in area, i.e., 2,040 km2. During the four periods, A. chinensis + forbs steppe was the widest distributed land cover type in 1987 and 1991, with its area was 5281.2 km2 and 4104.3 km2, respectively. However, in 1997 and 2000, S. krylavii was the most widespread land cover type with an area of 4,109.6 km2 and 4,479.1 km2.