In this project, the soil and water loss of the sample region, the Loess Plateau of China, has been studied systematically, synthetically and macroscopically; series of quantitative indices have been set up to assess the soil and water loss of this region; GIS is used to analyze the factors of soil and water loss spatially, to aggregate the data with different origins and to extract the thematic information; the mathematical model is set up to assess the regional soil loss and finally some application results have been got.