Abstract: Based on the water scouring experiments in forage grass slope and the naked one(control),water infiltration and the generation process of runoff and sediment were studied,and the effects and hydrodynamic characteristic mechanism of grass on the reduction of runoff and sediment were analyzed quantitatively.The results showed:1) the process figure of water infiltration was coincide with Horton formula:i=i_c+(i₀-i_c)e^-kt in both grass slope and the control;in comparison to the control,runoff coefficient and sediment transporting rate decreased by 28.3% and 78.4% in the grass slope,respectively.Water infiltration rate increased by 40% and runoff initiation put off 2.5 min;2) the curve of sediment transporting on the control slope showed high-low-high trend,while it increased first and then decreased on the grass slope;3) the flow regimes in grass slope and the control belong to laminar flow and tardigrade flow,respectively,which proves that the capability of resisting soil erosion and sediment movement in grass slope is stronger than that in the control;although the grass slope shows low runoff velocity and high resistance coefficient as well as roughness coefficient,its runoff depth is equal to that of the control.