Through simulation of rainfall in laboratory, the impacts of different straw coverages (0%, 25%, 50%, 75%, 100%) and different slope gradients(25°, 30°, 35°) on the slope erosion of colluvial deposits were disclosed under the condition of 60 mm/h rainfall rate. The main results showed that: 1) The initial time of runoff under different conditions changed from 49 s to 913 s. The initial time of runoff would be putted off with the increase of straw coverage under the same slope gradient. The initial time of runoff was longest at 35° but shortest at 30°. The initial time of runoff was positively correlated with straw coverage. 2) At the beginning of raining, the runoff ratios increased rapidly in a short time, then slowed down gradually. The range of runoff increased with the increasing slope. 3)The runoff ratio was higher at 30° than at 25° and 35° under the same straw coverage. The critical straw coverage of sediment yield was 50%.