Supported by GIS, Universal Soil Loss Equation(USLE) was used to estimate soil erosion in different geopedologic units interpreted from air photos at approximate scale of 1∶20 000. Based on field surveys,a land use map was interpreted from TM image(1991-11-17)by supervised classification for estimating p factor. Likewise, TM image was also applied to calculate land cover rate for estimating C factor. According to the analysis of cropping system and intra annual precipitation distribution, three periods of October to March (Ⅰ), April to June (Ⅱ), and July to September (Ⅲ) with distinguished land cover differences were identified.Land cover rate for period Ⅰ was calculated from TM image through a normalized difference vegetation index (NDVI), and land cover rate for the other two periods were modi fied from that of period Ⅰ by considering the land use types. A weighted average of land cover rate was calculated from that of three periodsby considering the distribution of precipitation.The result shows that the relation between the estimated value and observed value is high when land cover rate is over 15%.