Abstract: Danjiangkou Reservoir area is the core water source area of the middle route of the South-to-North Water Diversion Project.In order to continue promoting the pollution prevention and ecological environmental protection along the water transmission line and the water-receiving area, a comprehensive evaluation and analysis method was used to investigate and sample the groundwater environment in the water source area.The results showed that:(1) There were 20 potential pollution sources in the Danjiangkou Reservoir water source area, including 12 domestic garbage dumps, 4 tailings reservoirs, and 4 closed pit mine wastewater.(2) Among the 126 groups of groundwater samples, Class Ⅲ water accounted for the highest proportion of 30%,followed by Class Ⅱ water and Class Ⅳ water, both accounting for 24.5%,Class Ⅴ water accounted for 19%,and Class Ⅰ water accounted for the lowest proportion, only 2%.There were 24 groups of severely polluted Class Ⅴ water, which mainly distributed in Yunyang District and Zhushan County.The main exceeding indicators in Yunyang District were nitrate, aluminum, etc.,and the main exceeding element in Zhushan County was zinc.There were 31 groups of moderately polluted Class Ⅳ water, mainly distributed in Fangxian County and Danjiangkou City, and the main excess element in Fangxian County was iron and the main excess index in Danjiangkou City was nitrate.(3) The indicators with high excess rate in groundwater were iron(18.0%),nitrate(12.5%),aluminum(11.7%) and zinc(10.9%).The results of this research can provide basic support for the ecological and environmental protection of Danjiangkou Reservoir water source area.