Intercropping is an important practice for controlling soil erosion in the world. However, knowledge on this phenomenon is not well understood, especially in flow hydraulics. A lab experiment was conducted to provide the theoretical basis for reducing erosion mechanisms in intercropping. Three cropping patterns i.e. maize monoculture (MC), potato monoculture (PC), and two rows of maize intercropped with two rows of potato (IC) were used under two surface roughness models:low ridging and high ridging, totaling six treatments. The runoff velocity, Reynolds number, Froude number, and Darcy-Weisbach resistance coefficient were measured with two rainfall intensities (40, 80 mm/h) during the experimental periods. The results suggested that:(1) The values of IC were lower than those of MC in terms of runoff velocity, Reynolds number, and Froude number. Furthermore, the resistance coefficients in IC were higher than those in MC at the same rainfall intensity. There was no difference between IC and PC in terms of runoff velocities and resistance coefficients. In early July, the resistance coefficients were 0.41~0.53 for IC and 0.09~0.10 for MC at the rainfall intensity of 80 mm/h. The runoff velocities was 0.11~0.12 m/s for IC and 0.19~0.21 m/s for MC at the same rainfall intensity.(2) The lowest runoff velocity, Reynolds number, and Froude number were observed in intercropping with high ridging, which gave the highest resistance coefficient. In early July, the runoff velocities of intercropping with high ridging, intercropping with low ridging, and maize monoculture with high ridging were 35.71%, 35.71% and 14.29% respectively lower than that of maize sole crop with low ridging at the rainfall intensity of 40 mm/h. Thereby, intercropping could increase resistance coefficient to reduce runoff velocity, which was one of mechanism to reduce erosion in intercropping and provide an important reference for understanding the mechanism of soil erosion controlling by crop cultivation. In addition, intercropping with high ridging could effectively decrease runoff velocity on the surface, and might be contributed to the soil erosion control and sustainable development of agriculture.