Abstract: The analysis and simulation work concerning rainfall infiltration and motion equation of slope runoff are carried out based on achievements of related research subjects based on the theories of infiltration and flow fluctuations. The influence rules of runoff time and production flow are deduced. The influencing factors include rainfall intensity, permeability coefficient , soil suction, compactness , water content, Manning's roughness coefficient, slope gradient and slope length . The results show the rainfall intensity has more impact on the runoff time and production flow. In prolonged rainfall, the slope length affects the cutting slope. In short rains, the larger roughness and slope decrease are the important factors to reduce the runoff.