Abstract: Inflow of external water into the drainage pipelines impacts the efficiency and energy cost in sewage treatment works, which also increases the risk of overflow and environmental pollution. This study aims to establish a water quality characteristic factor library for the drainage network of Foshan City, providing scientific reference and technical support for the subsequent identification of external water infiltration. Through a comprehensive analysis of the functional areas of a typical region of the city, five waters were identified for subsequent analysis, including domestic sewage, industrial wastewater, agricultural water, river water, and rainwater. Situ sampling and laboratory measurement were conducted to determine the water quality characteristics of these waters. Total phosphorus and nitrogen, chemical oxygen demand and manganese, nitrate, dissolved organic carbon, and salinity were determined as the characteristic factors for the five waters, respectively.