Abstract: In recent years, water quality monitoring technology has been frequently used in the diagnostic inspection of sewage pipeline health.This paper aims to study the application of novel quantum dot spectral sensing technology to monitor water quality and investigate pipeline health in the upstream sewage network of a wastewater treatment plant in Wuhu City.The investigation studied illicit connections(pipe network wrong mixing and rainfall connecting to sewers)and external water infiltration.In this study, two key areas leading to low quality of inflowing water in the sewage treatment plant were identified.The source of external water infiltration was located and verified on site through the fine monitoring of the sewage pipe network in the key areas.Results show that through the joint analysis of water quality data or water quality and flow, rainfall and other data, the new in-situ water quality online monitoring technology can play an important role in the field of pipeline network investigation and background concentration characteristic monitoring, which is conducive to improving the quality and efficiency of the sewage system and reducing the overflow pollution discharge.