Abstract: The polder in the tidal flats of the Huai River main stream affect the flow capacity of the river channel. This article uses MIKE series software to establish a one-dimensional and two-dimensional coupled hydrodynamic model for the section from Bengbu Sluice to Xiaoliuxiang in the Huaihe River main stream, simulates the flow field in the Yan'ganwei area, analyzes the main reasons for the impact of Yan'ganwei on flood discharge, calculates the impact of different embankment retreat scales on reducing the water level of the main stream of the Huaihe River under design flood and moderate flood conditions, and analyze the investment and benefits of engineering schemes. The results showed that when the retreat distance was 350 meters, the adverse water conditions such as backflow and the water blocking effect of the embankment could be basically eliminated, and the cost-effectiveness ratio was optimal. Continuing to increase the retreat distance had no significant effect on reducing the water level of the river channel.