Abstract: Under heavy rainfall conditions, over-input fertilizers and chemicals with surface runoff through the catchment area flow into surface water and groundwater such as rivers and reservoirs, causing water eutrophication. Controlling soil and water erosion through ecological measures is an important way to deal with non-point source pollution in these areas. The ecological functions of vegetation buffer zones and the mechanism to reduce non-point source pollution were discussed in water source areas, which will provide scientific basis and technical support for non-point source pollution prevention and water environment improvement. The published papers related to vegetation buffer zones and non-point source pollution were collected and discussed. The mechanisms included: ① the absorption of nitrogen and phosphorus by plants; ② vegetation to consolidate soil and reduce soil erosion; ③ vegetation coverage prolonged the residence time of runoff on the ground, increased water infiltration, and reduced the loss of nitrogen, phosphorus and other substances with surface runoff; ④ plant roots participated in various physical, chemical and biological processes in the soil, accelerated the morphological transformation of carbon, nitrogen, phosphorus and other substances. Some suggestions have been pointed out according to the characteristics of water source non-point source pollution.