Slope hydrology is an important branch of Modern hydrology, it has a great significance to study the runoff and converge mechanism research of the basin. The characteristics study include of runoff velocity and infiltration rate etc al. the runoff velocity is an important physical quantity to describe overland flow hydraulics characterize. This paper study the effect of slope degrees and water drainage amount on the runoff velocity. The result shows: slope degree and water drainage both are the important factors to change the runoff velocity. The average runoff velocity were increased first and then reach steady-state fluctuations between 0.1-1m/s at different drainage amount, the time they got to the steady states was different. The results could provide some technology support to establishment slope erosion model.