Abstract: Abstract: The quantitative study of soil erosion and nutrient loss in a small watershed can provide an important basis for ecological protection, soil, and water conservation, and ecological compensation in the water source areas of the South to North Water Diversion Project. Revised universal soil loss equation (RUSLE) was used to estimate the soil erosion and nutrient loss supported by the geographic information system (GIS) in the Yingwugou watershed; however, the soil erosion intensity of the study area was classified. The results indicated that the annual soil erosion modulus in the Yingwugou watershed was 3140 t/km2. This falls in the category of moderate degree erosion. The area above high soil erosion intensity only accounted for 24.1% but the soil erosion amount was 4573.0 t, which accounted for 84.8% of the annual soil erosion amount. The high soil erosion area was mainly distributed in sloping cropland with big slopes, which was the key management area. Soil erosion amounts under different land-use types showed great differences. The annual soil erosion moduluses of forestland, grassland, and cropland were 509.7, 1511.8, and 4606.5 t/km2, respectively. The annual soil erosion amount of forestland and grassland was relatively small and the annual soil erosion amount of cropland accounted for 95.3% of the total soil erosion amount in the study area. For each additional 5° slope, the increased soil erosion modulus of different land uses was 1 to 2 times greater than that of each additional 5m for slope length. The annual loss amount of total nitrogen, total phosphorus, and organic matter in topsoil was 3.81, 3.52, and 101.45 t, respectively. The nutrient loss of cropland was serious. The annual loss moduluses of total nitrogen, total phosphorus, and organic matter with sediment were 1.01, 0.75, and 38.43 t/(km2×a), respectively. The study could provide a scientific basis for the control of soil erosion and water loss, non-point source pollution, and the construction of clean, small watersheds in the water source area.