The investigation of sloping farmland, especially that with slope steeper than 25°, is an important task in soil resource investigation and evaluation during the development of western China. DEMis a digital elevation model produced by computer system. It can make topographic analysis, simulate geomorphologic shape, and display geomorphologic characteristics and topographic position directly. With the 1:10000 scale relief map as an example and under the support of Arc/Info software of GIS, the authors formed DEM through digitizing the topographic contour map. The slope map computed and derived by the DEM was taken as the basic material and, with the integration of the landuse map and related material and the application of GISto comprehensive analysis, the data of sloping farmland were obtained. In the whole process, computer processing occupies the dominant position and human interference is suppressed. Therefore, the efficiency is high.