In recent years, increasing human activities and infrastructure development in Southeastern Tibet have intensified soil erosion problems. To investigate the characteristics of soil erosion in small watersheds within this region, this study selected the Zhongdui watershed as the research area. Based on the GeoWEPP model, 28 sub-watersheds were delineated. Combined with field investigations, simulations were conducted to estimate runoff and soil erosion generated by single rainfall events and annual precipitation for the years 2000, 2005, 2010, 2015, 2020 and 2022. The spatial distribution characteristics of runoff processes and sediment transport pathways under surface disturbance were analyzed, and soil erosion risk zones were identified. The results showed that: (1) High annual runoff and severe soil erosion in the Zhongdui watershed mainly occurred from May to October. With the expansion of human activities and surface disturbances, runoff and soil erosion in 2015, 2020, and 2022 were significantly higher than in earlier years. (2) Sediments transported at the watershed outlet were dominated by particles ranging from 0.14 to 0.20 mm, with fine silt prevailing in the middle reaches of the river and coarser sand particles at both ends. Areas with severe soil erosion were mainly distributed in the steep eastern slopes, as well as the middle and southern parts of the main channel, showing an increasing trend from northwest to southeast. (3) The proportion of high-risk soil erosion zones increased markedly in 2010 and 2015, while from 2020 to 2022, the proportions of low-, medium-, and high-risk zones decreased, and the extremely high-risk zones increased. The erosion risk zones migrated from the northwest to the southeast of the watershed. Land use, slope, and human disturbances jointly influenced the spatial distribution of soil erosion risk within the watershed.These findings provide a scientific reference for soil erosion control and management in Southeastern Tibet.