Objectives The filtering and feeding characteristics of Hyriopsis cumingii were used to monitor and improve the water quality to provide an eco-friendly method for improving the water quality of X River. Methods The middle section of X River urban area was selected to conduct the experiment for 7 months. Multiple aquaculture plots were set up within the experimental area, and a certain number of Hyriopsis cumingii were released into each aquaculture plot. Indicators of water quality including chemical oxygen demand, ammonia nitrogen, total nitrogen, and total phosphorus in the experimented area were regularly monitored, and their effects on improving water quality were evaluated. Results The water quality in the experimented area was significantly improved, and indicators including chemical oxygen demand, ammonia nitrogen, total nitrogen, and total phosphorus all decreased after aquaculture for 7 months. After 150 days, the chemical oxygen demand, ammonia nitrogen and total phosphorus in the downstream area of the experimented area decreased from 25.6 mg/L (120 days) to 22.0 mg/L (210 days), from 0.99 mg/L (120 days) to 0.18 mg/L (210 days), and from 0.17 mg/L (120 days) to 0.07 mg/L (210 days), respectively, reaching the surface water standard of Class Ⅲ. Conclusions It is indicated that the use of Hyriopsis cumingii for monitoring water quality can solve the problems of abundant plankton and low water transparency in the river..