Abstract: To improve the water quality in rivers in Yunbei main urban area of Changzhou City, a study of clean water diversion to improve the water environment based on numerical simulation and field test was conducted. The water source, water diversion pattern and quantity of water diversion were determined according to the regional topography and river system. Based on current engineering conditions, a clean water diversion scheme was proposed including "making use of the high quality water source of the Yangtze River, building two clear water channels, building four new movable overflow weirs and forming three-stage water levels." Based on Infoworks ICM, the hydrodynamic mathematical model of the main urban area of Changzhou city was constructed. Through this model to simulate the distribution of river flow in the main urban area of Changzhou city under different schemes, the Zaogang river level was changed from 3.80~4.00 m, and the optimal entry level was determined. Based on the field test, the effect of hydrodynamic enhancement and water quality improvement was verified. The results indicate that most of the river flow increased significantly, the flow rate reached 7 cm/s or more, and many water quality indicators reached Class Ⅲ and above after the implementation of the clean water diversion scheme of the main urban area of Changzhou city. The research results can provide references for water environment improvement in other plain river network areas.