Abstract: By collecting measured data on water depth, topography, ocean currents, and tide levels in the vicinity of Dingzi Bay, numerical simulation methods were used to study the sedimentary dynamic characteristics of different schemes of cross-sea bridge construction in the eastern part of Dingzi Bay, including hydrodynamics, tidal capacity, water exchange, and topographic erosion and deposition, using the Mike21 numerical simulation software. The impact of the cross-sea bridge construction on the dynamic sedimentary environment in the surrounding waters of Ludao Island was studied. Results indicate that the construction project would significantly reduce the tidal current velocity in the surrounding waters of Ludao Island by a decrease of about 50%. The construction project could increase the siltation intensity around Ludao Island, with a maximum increase in siltation rate of about 6 cm/a. The construction may significantly affect the water exchange around Ludao Island, resulting in a decrease in water exchange rate. The area with water exchange rate greater than 80% would be decreased from 73.1% to 66.9%, and the average decrease in tidal capacity during high and low tides would exceed 10%. Overall, the recommended bridge lengths on the north, middle, and south sides are 100 m, 100 m, and 200 m, respectively. The recommended scheme can fully utilize the existing waterways, and thus it is superior among all the schemes in terms of hydrodynamics, water exchange, and tidal capacity, with the minimal impact on the marine environment. The recommended scheme will maximize the coordinated development of engineering construction and marine environment.