In order to understand the law of overflow pollution in Lecong Town, this paper conducts research on the overflow characteristics and pollution control of the sewage pipe network and carries out two cycles of monitoring on sunny days and rainy days. At the same time, a detailed plan is developed to analyze the Lecong Town sewage pipe network. The study finds that the peak of pollutant concentration during the rainfall period in Lecong Town appears in the initial 20mm; after calculating the amount of pollutants, it is found that the overflow pollutants in the initial 20mm rainfall takes a larger proportion up to 66% in the output of river water. It can be seen that the generation of sunny-day overflow pollution in Lecong Town is due to the backward flow of river water into the pipes, causing domestic sewage unable to be treated normally. At the same time, the river water in the pipe also directly affects the generation of rainy-day overflow. Improving the flow of river water into pipe network is the primary way to control the pollution of sewage overflow.