[Objective] In order to determine the optimal plant configuration of slope ecological protection, we designed a washout test by control the velocity and flow of water in runoff plots of different surface type. [Methods] Based on experimental data, we studied the effect of different surface types on both surface roughness coefficient and hydraulics characteristic parameters. [Results] (1) The effect of herbaceous vegetation on the velocity of the block is better than shrub tree species. Populus tomentosa promote the surface velocity. (2) The largest average roughness coefficient is in the lawn plot, the smallest is bare plot. Laying litter in bare ground can effectively increase the surface roughness coefficient value and there is no significantly change by laying gravel. (3) Reynolds coefficient(R_e) is 21.34~23.49 and the largest is the litter surface, the smallest is Populus tomentosa surface. Water flow is laminar flow, the turbulence is weak, Froude coefficient(F_r) is 0.35~2.55, Darcy-Weisbach resistance coefficient(f) is 1.03~54.43. [Conclusion] The bare land with litters and grassland surface can effectively resist runoff scour and the Populus tomentosa underlying surface has the potential to cause the most amount of soil erosion.