Abstract: Abstract: Slope runoff of colluviums is the premise for gully runoff erosion, and is the main mode of the sheet-flow erosion in Benggang basin. Studies on characteristics of slope runoff and sediment transportation mechanism in Benggang basin are important for understanding Benggang erosion process and for erosion prevention and control. In this study, an artificial rainfall simulation experiment was carried out in field to investigate the slope runoff process and soil moisture distribution in Benggang basin. Liantanggang Benggang in Wuhua County of Guangdong Province was taken as the study area. In this area, 7 different colluvial deposits were selected including old and new deposits. The 7 deposits had slope of 4o-48o. The old deposits were developed for more than 5 years with dark color and the new deposits were less than 5 years with pale red color. In general, the structure was more stable in the old deposits than the new deposits. These 7 deposits were used for observations of runoff time under the artificial rainfall simulation. A portable rainfall simulator was used with rainfall duration from 0.6 to 60 min and rainfall amount from 2.4 to 60 mm. A total of 28 simulated rainfall experiments were preformed in the field, and the runoff time as well as soil moisture were observed and measured. The results showed that: 1) A negative power function could describe the relationship between the rainfall intensity and slope runoff (P＜0.01), and the runoff time decreased rapidly with the increase of rainfall intensity; 2) A negative logarithmic function could reveal the relationship between runoff time and initial soil water content in depth of 10 cm for the old colluviums; 3) Based on the initial soil water content and rainfall intensity, the 3D surface model may be used to estimate the runoff time of the colluviums; 4) When the rainfall intensity reached 3.5 mm/min or above, the runoff time showed a linearly negative correlation with the slope of the colluviums, and the runoff time became shorter with increasing slopes. 5) After runoff of the colluviums, soil moisture was obviously different between the old and new deposits at the depth of 10 cm, and the soil moisture was over 20% in the old colluviums, and less 20% in the new colluviums; and 6) In the end of precipitation and after 24 h of rainfall, the wetting depth of the new colluviums were higher than that of the old colluviums, indicating that the instable depth of the new colluviums is larger than that of the old colluviums when rainfall occurs. The results provide rich information for understanding slope runoff process and method for erosion forecast in Benggang basin.