Taking the Xueshi River in Ancient District of Suzhou City as the research object, this study analyzed the impact of initial rainfall runoff pollution on river water quality under the existing scheduling scheme. A hydrological-hydrodynamic-water quality coupled model was constructed based on the SWMM and MIKE11 models and used to simulate the changes in river water quality under different scheduling schemes. Furthermore, optimal scheduling schemes for improving the water quality of the Xueshi River after rainfall under different rainfall conditions were proposed. The results show that the overall water quality of the Xueshi River is good, but it degrades to Grade Ⅳ during heavy rain and rainstorm events. The initial rainfall runoff pollution has the most significant impact on the river water quality during heavy rain, while its impact lasts the longest during rainstorm. The constructed coupled model achieves good simulation results for water level, flow rate and water quality at each monitoring section. Through the design of working conditions, appropriately increasing the gate flow during heavy rain and rainstorm periods can significantly reduce the peak mass concentration of NH₃-N in the water body, stabilizing the water quality to Grade Ⅲ standard and thus effectively improving the river water quality after rainfall.