Herbal buffer zone can effectively intercept pollutants such as sediment, total nitrogen, total phosphorus and other pollutants on slope, which is one of the main measures to prevent and control agricultural non-point source pollution. The surface runoff was simulated by artificial water distribution, and the effects of different runoff on interception capacity of herbaceous buffer zone were studied. The results showed that the herbal buffer had a certain reduction effect on pollutants. The herbal buffer had the best effect on sediment reduction and the worst effect on total phosphorus reduction. White clover had a stronger ability to reduce pollutants than ryegrass. Runoff had a greater impact on the reduction rate of total nitrogen and total phosphorus in herbal buffer zone, but a little impact on sediment reduction rate. When the flow rate increased from 0.08 L/s to 0.24 L/s, the reduction rate of total nitrogen and total phosphorus in herbal buffer zone decreased to 9% and 6%, while the sediment reduction rate was 34%. With the increasing of discharge scouring time, the concentration of total nitrogen, total phosphorus and sediment in the outflow decreased and gradually reached a stable level. When the flow rate increased to 0.24 L/s, the concentration range of total nitrogen and total phosphorus were 11.5~24.7 and 1.6~2.3 mg/L, respectively. There was no significant difference in sediment concentration under different flow rates. In this study, the removal of total nitrogen and total phosphorus by herbal buffer zone was greatly affected by the flow rate, and the buffer zone had no removal effect on total nitrogen and total phosphorus at large flow rate, but the removal of sediment by buffer zone was less affected by the flow.