Abstract: Using simulated rainfall experiment under different conditions（rainfall intensity: 1.5 and 2mm/min, slope gradient: 10°,15°,20°and 25°, slope length: 5 and 10m), the interaction effects of slope, rainfall intensity and slope length on rill erosion were studied by establishing the regression models. The experimental results indicated that: Runoff producing rate per unit width was chosen as the characteristic index of runoff, both rainfall intensity and slope had significant positive effects on it, while the interaction effect of slope and slope length was significant as well. Changes of sediment concentration were mainly determined by slope gradient and rainfall intensity, while the effect of slope length was not significant. Rainfall intensity, slope and slope length had positive effect on velocity of interrill sheet flow, while the effects of these factors on velocity of rill flow were also significant, in addition, the interaction effect of slope gradient and slope length has a significant negative effect on the velocity of rill flow.