Abstract:Taking Pingzhai Reservoir Protection Area and Quasi-protection Area as the study object, we collected 59 water samples from the trunk stream section and 41 ones from the branch stream section, and 88 soil samples to analyze and evaluate the situation of non-point source pollution in the basin, and made a space analysis by GIS. The results show that, in the low water period, the water quality of class I accounted for 59. 62% in all water samples, class Ⅱ~Ⅲ accounted for 15. 38%, class Ⅳ accounted for 5. 77%, class V accounted for 9. 62%; In the high water period, the ratio of class IV water was as much as 72. 92%, classⅠ~Ⅲ accounted for 22. 91%, class V accounted for 4. 17%, and the main index exceeding standards are TN、NH3-N and TP, showing a typical characteristics of non-point source pollution. The weights of land utilization factor(L)、runoff factor(Q)and distance factor(D)were determined by the modified TOPSIS, getting the risk assessment index of non-point source pollution. The research areas were divided into 4 categories of sensitive control areas according to the risk assessment index. Among them, moderately sensitive areas was mainly distributed in the slope farmland near the river, so we should adjustment planting structure and strengthen the management of fertilizer and other agricultural chemicals in these areas. Highly sensitive regions were mainly distributed in urban residential areas, the main source of pollution were the urban sewage and coal mining wastewater, so we should promote the construction of urban sewage and coal mine wastewater disposal system.