Abstract: In order to provide certain scientific basis and decisive support to the study of rock desertification development and evolution in southwest China karst area, this paper takes the Maoeun karst underground river basin in Guilin as the study area and uses RS image of two different periods to extract information from three main natural factors that affect soil erosion - slope gradient, vegetation coverage rate and land-use type. Furthermore, GIS is used as the analysis platform to compare the soil erosion condition in two periods in the study area ,making reference to classification standard of soil erosion intensity. The result shows that the steeper the slope the easier and more intense the soil erosion and the vegetation coverage rate also controls soil erosion intensity. In order to restrain and diminish soil erosion area, the vegetation must be protected and turn more arable land back to woods. As to the land-use type, because it changes slowly, so it doesn＇t make great effect to the soil erosion intensity. It is proved that the study on RS can provide reference for the local economic development, supervision,evaluation and forecast as well as administration of soil erosion.