In order to explore the mechanism of rill erosion process on alpine soil slope in Southeast Tibet, establish the factor model of sediment transport capacity, and provide scientific basis for controlling soil and water loss on slope surface, this paper took the alpine soil in the Tibet Plateau as the research object, and carried out an indoor runoff scouring experiment. The results showed that: (1) The critical slope length of sediment transport capacity decreased with the increase of sediment transport capacity, ranging from 3.27 m to 8.31 m. When the slope was 15°~25°, the critical slope length was about 5.0 m. (2) Under different slopes, the sediment transport capacity increased with the increase of discharge, which could be well described by a linear equation (T_c=Aq). The influence of the same discharge on small slope was greater than that on large slope. (3) The sediment transport capacity and slope could be well expressed by an exponential equation (T_c=-ae^(-S/b)+c). With the increase of slope, the sediment transport capacity increased rapidly at first, and then gradually leveled off, and increased gently when the slope reached 15°. (4) The sediment transport capacity could be expressed by a two-dimensional power function equation T_c=1697.83S^0.491q^1.043. Compared with other models, ANSWERS model was not suitable for calculating sediment transport capacity of Alpine soil, but the performance of Zhang model, Gao model and Lei model were as good as this model.