Abstract: In order to investigate the flood impact characteristics of bridge engineering, this paper takes the flood control impact assessment of a specific project as an example. The MIKE21 numerical model was employed to calculate the backwater level at the bridge front, flow velocity, and changes in the flow field under different flood frequencies for the Lishui Grand Bridge. The results indicate that under both the designed flood control level and the historical maximum flood conditions, the maximum water level upstream of the bridge site increased by 2.22 cm after construction, while the maximum flow velocity near the bridge piers decreased by 0.39 m/s. The local flow field near the engineering area was deflected to both sides of the bridge piers, with the impact limited to the vicinity of the project. The findings provide an important reference for the assessment of flood control impacts on bridge structures.