This literary grace uses the on trial method that the indoor artificial simulated rainfall,analysis the velocity spatial distribution of the thin layer flow with the time on different form slopes.Main research result is as follows: The velocity of flow,on the condition of the same rainfall intensity and slope gradient,the linear form slope is the biggest,the convex form slope the next,and the concave form slope the least.Under the condition of the same slope form,the slope surface current velocity is increases with the rain intensity and the slope gradient.And then,slope surface current velocity is different in different form slopes.But the general rule is that the slope surface current velocity is increases with the increase of the rainfall intensity and the slope gradient.