[Objective] The change rules and characteristics of the surface roughness was analyzed under the station of submerged and unsubmerged and the different vegetation density in order to provide the reference for studying the effect of vegetation on the surface roughness.[Methods] The plastic rods, as a surrogate for vegetation distribution, were used to simulate two different densities in the flushing experiments.[Results] The earth surface roughness changes were different between the submerged vegetation and unsubmerged vegetation. Under the unsubmerged condition, the earth surface roughness decreased with the increase of the average water depth.While submerged depth was low, the earth surface roughness firstly increased and then decreased with the increase of the average water depth. When the submerged depth was very deep, the earth surface roughness tends to be a stable value.[Conclusion] The earth surface roughness value increases along with the vegetation density. Under the same underlying surface, the surface roughness value changes with different flow direction.