[Objective] The influence of water-related structures on the flood routing process before and after structure construction was analyzed to provide scientific supports for the real and efficient calculation of bridge engineering in flood storage and detention areas, and for the effective development of flood control in flood storage areas. [Methods] The Mengwa flood storage area in Fuyang City, Anhui Province was selected as the study area. Based on the latest data of regional topography, hydrological data, and bridge engineering design, the unstructured hydrodynamic model of MIKE 21 was used to simulate the flood evolution process of the Mengwa flood storage area in real time. The influence of bridge construction on flood evolution time, velocity distribution, and water level change in the flood storage and detention area was analyzed. [Results] After the construction of the bridge project, the flood-splitting time near the bridge position was 45 s behind the maximum lag before the construction of the project; the flow rate distribution range of the mainstream area was 0.4 to 0.6 m/s; the local velocity change rate was 7.409%; the maximum elevation value of the water level near the bridge was 0.006 m; and the maximum change rate of the water level was -0.22‰. [Conclusion] Bridge construction delayed the flooding time in the flood storage area, raised the water level near the pier, and changed the distribution of the flow rate near the project. However, the overall impact on the flood storage area was small, and basically did not affect the normal operation of the flood storage area.