Abstract: In order to explore the characteristics of the hydrodynamic water quality of Hengshui Lake, a two-dimensional hydrodynamic water quality model of Hengshui Lake was built based on the Environmental Fluid Dynamics Code (EFDC) model on the basis of field investigation. The model was calibrated and validated using observation data such as water level, temperature, and water quality from 2018 and 2019, respectively, to better reflect the hydrodynamic and water quality conditions of Hengshui Lake. The characteristics of the hydrodynamic and water quality changes in space and time of Hengshui Lake were simulated, and the driving mechanism of the hydrodynamic water quality evolution of the lake was analyzed. The results showed that the hydrodynamic force of Hengshui Lake was weak, and water replenishment was an important way to improve the hydrodynamic force, which had a promoting effect on maintaining the ecological water level of the lake and improving the water exchange capacity. The large amount of nutrients brought in by water replenishment had a significant impact on the water quality of the lake area. The water quality indicators at various stations fluctuated greatly during the water replenishment period, with Wangkou Gate and Xiaohuxin stations being greatly affected. In the case of poor inflow water quality, water replenishment could easily aggravate lake water pollution, and control of inflow water quality could not be ignored.