Abstract: Non-point source pollution, also called diffuse source pollution, mainly caused from the soil erosion and sedimentation, livestock wastes, and agricultural land (pesticide and other poisonous chemical components).In this article, the physical process of soil erosion was described, the main factors which would affect the soil erosion process were discussed, and the non-point source pollution (NPSP) model, which consists of the rainfall-runoff sub-model, the soil erosion sub-model (American USLE), and the livestock wastes sub-model, was constructed.Finally, the experiences and conclusions of the NPSP application in the Dodder Basin of Ireland was introduced.