Abstract: In light of the fact that the concentration of sewage influent of the urban sewage treatment plants in the north shore of the lake has decreased year on year since the implementation of the sewage interception project, and that the rainwater and sewage diversion failed to meet the expectation, through onsite investigation, tracking and monitoring influent conditions, this paper explored the impact factors such as the incomplete diversion of rainwater and sewage, the integrated urban-rural sewage collection mode, rainfall during sewage interception project construction, the expansion of sewage interception range, the increase of sewage interception facilities, as well as the mixing of groundwater and farmland drainage, daily supervision mechanism and the involvement by the public. Based on this, the paper proposed targeted countermeasures and suggestions for future referenc.