[Objective] The effects of rainfall intensity and slope gradient on runoff process were studied to provide scientific basis for soil and water conservation control on purple soil areas. [Methods] Researches were studied based on indoor artificial rainfall simulation experiments. [Results] Runoff courses could be generally divided into concave and convex type, and can be described by exponential function and log function, respectively. With the increases of rainfall intensity and slope, the runoff initiation time decreased, the runoff amount increased, and the runoff course became similar. At low rainfall intensity, the effect of slope gradient was obvious in runoff generation, while at high intensity, the effect decreased. In this case, slope gradient was the main factor at low rainfall intensities(33,54 mm/h), while rainfall intensity became the main factor at high rainfall intensity(94,125 mm/h). [Conclusion] Both rainfall intensity and slope gradients were the main factors of hillslope erosion. With the increase in rainfall intensity, the hillslope erosion became more sharply. And the main erosion factor transferred from slope to rainfall intensity.