In order to treat the polluted water source of Longdong spring in Qingganglin village, it was necessary to find out the recharge relationship and concentrated runoff channel of local karst groundwater of longdong spring. Groundwater tracer technology was widely used in identifying the development and distribution of karst pipelines and determining the underground river system. According to the hydrogeological conditions of the tracer test area, the dropping hole 5, which had a hydraulic connection with Longdong spring, was selected as the launching site, and the receiving point was set up in Longdong spring, and salt and luciferin were used as tracers. The tracer results showed that there was an obvious hydraulic connection between the underground river in dropping hole 5 and Longdong spring, and it supplied longdong spring. There was a channel between dropping hole 5 and Longdong spring that led to the polluted water source and Longdong spring of the mine.