In order to explore a feasible scheme for improving the water quality of a plain river network in Weitang Town of Suzhou, a hydrodynamic and water quality coupling model of the river network was constructed based on Delft3D. Using Delft3D-FLOW, the spatiotemporal characteristics of the hydrodynamics in the river channels of the town during October of 2021 were simulated, and the discharges of the water pump stations and water thrusters were demonstrated. Using the Delft3D-WAQ module and tanking CODMn, NH3-N, and TP as the main evaluation indicators, the rationality of the scale of bypass purification facilities was demonstrated. The simulation results show that the hydrodynamic results of the model are relatively ideal and the live water effect is good. The discharge of the No.1 Pump Station in the Laozhen section is determined to be 1.0 m³/s, and the in duced discharge of the live water thrusters in the Pearl Lake section is 0.4 m³/s in each group.The water quality simulation results are relatively ideal. After being treated with Pearl Lake and Diamond Bypass purification facilities with a scale of 20 000 m³/d, the water quality of the rivers in the town can reach to Level IV of the Environmental Quality Standard for Surface Water (GB.3838—2002), with significant improvement effect.