Comprehensively considering the erosion of red soil slope with herbaceous vegetation,indoor simulated rainfall experiments are carried out to discuss the anti-erosion effect with different slopes and different vegetation coverages of red soil slope in heavy rainfall(2.0 mm/min)and short duration(30 min). The results show that with the increase of vegetation coverage,the erosion reduces rapidly within the vegetation coverage less than 40% while the erosion reduces gently as the vegetation coverage more than 60%,so the critical vegetation coverage is 40%-60%;The critical slope changes for different vegetation coverages,The critical slope reduces within the vegetation coverage less than 40% while The critical slope disappears as the vegetation coverage more than 60% because the erosion increases gently. The reason led to this phenomenon is that the critical slope can be effected by soil properties,vegetation coverage,rainfall and so on.