With the implementation of the National Action Plan for the Great Protection of Yangtze River, it is urgent to treat the black and odorous water in the first tributary of the Yangtze River Basin so as to achieve the goal of "clear water and green shore, fish soaring on shallow bottom". The Huaxi River in Chongqing is one of the first tributaries of the Yangtze River. In view of the overflow pollution of the combined tank culvert in the comprehensive treatment project of Huaxi River, the treatment idea of "separated reconstruction of rainwater and sewage at the source + construction of water quality purification station at the end" is put forward. The design scale of the Tuqiao Water Quality Purification Station is 10 000 m3 /d, the design volume of storage tank is 11 000 m3, and the effluent shall comply with quasi-Class IV standards. The operation result after completed shows that under the different working conditions of the combined sewage flow from the box culvert of Tuqiao, the operations of this station are normal by taking the treatment measures of terminal interception, storage and purification. The discharged sewage all researches the discharging standard, and is discharged externally to Huaxi River.