We use two-dimensional shallow-water tidal equation，obtain the real tidal flow field of Puba Port on the basis of model verification against the field measured data，and analyze the effect of the Puba Port bridge project on the flow and silt in the nearby sea area and the change of water quality resulting from the dangerous goods into the sea. The results show that the increased zone of flow velocity is located between two main piers of the bridge and near the water，the reduced zone of flow velocity is located mainly in the nearby waters of the southern and northern approach bridge piers and the local waters of the main piers. The deposition area mainly is located in the south part of the bridge of Puba Port and near the north part of the approach bridge，scour area is located in the waters around the main piers. If sulfuric acid leakage accident is produced in waters around the bridge，the affecting area of the water environment is large，such accident must be avoided to ensure the water quality.