Coastal engineering will influence hydrodynamics of neighboring waters. Based on a mathematical model with triangular grid and finite element, this study simulates the changing hydrodynamics of sea areas after the construction of sea-crossing bridge and embankments of the harbor highway. The results indicate that as the model can simulate hydrodynamics of waters with complicated topography, it can be applied to predicting the flow field change after the construction of coastal engineering, and provide a reference for future selection of computing models.