Abstract: To obtain an in-depth understanding of vegetation benefit in basin soil and water conservation, we have conducted laboratory tests on various relative hydrodynamics of overland flows ? relative flow velocity, relative flow depth, relative Froude number, and relative resistance coefficient ? using combinations of six slopes, seven flow discharges, and five types of vegetation coverage. The results show that as vegetation coverage or flow rate increases, both relative flow velocity and relative flow depth are increased and the vegetation effect in reducing flow velocity is enhanced. And the variation trends in both manifest a cut-off coverage of 4.7%. The vegetation effect on relative flow velocity depends much on flow rate but little on land slope, and flow rate are also independent of land slope. An increase in vegetation coverage or flow rate causes a higher relative Froude number and a greater capability of vegetation to weaken overland flow erosion. Relative resistance coefficient grows linearly with an increasing relative flow depth. This study would help the choice of vegetation measures and assessment of vegetation benefits in water conservation and sediment reduction.