Abstract: Regional land use change is an important part of global change. Located in the eastern part of Gansu Province, i. e., 35°15′～37°10′N, 106°20′～108°45′E, the Longdong region, an important part of the Loess Plateau in China, covers Pingliang and Qingyang prefectures, and has an area of 38259. 8 km².It is in a sem-i humid and sem-i arid farming-grazing ecotone, its ecological environment is vulnerable and is extremely sensitive to human activities. The rapid population growth and the social and economic development have resulted in a great change of land use in the region since the 1980's, which has also brought about a great impact to the ecological improvement in the whole Loess Plateau, rebuilding northwest China with the beautiful mountains and waters, and the great development of northwest China. Therefore, it is necessary and urgent to research the land use change in the Longdong region since recent decades by combining remote sensing with geographical information system (GIS). Based on the TM images of the years of 1986 and 2000 and by using the GIS software of ARC/INFO and ARVIEW, in this paper the information is extracted, the statistics and the analysis on the spatial distribution data are carried out, and the spatial change of the land use types and quality in the region during the period of 1986～2000 is discussed. The regional land use degree and the possible impact on the ecological environment are assessed. A theoretical basis is provided for the synthetic improvement of the land and the sustainable land use in the Longdong region.

Key words: Longdong region, land use change, remote sensing, GIS