The Shacheng Bay(SCB) is one of the most complex coastal bays in southeast China and due to the fact of complicated geometry and dynamic coastal processes, it is considered as a challenging area for the numerical simulation of its hydrodynamic characteristics. The most advanced finite volume ocean model, finite-volume coastal ocean model(FVCOM), has adopted to simulate this hydrodynamic system, where tidal currents, tidal residual current and dye diffusion processes were studied and analyzed quantitatively. The validation of this numerical model matches well with various observation data, including elevation and current data. The misfit of a tidal elevation has a relative standard error of 3.66% and 4.67% for M2 and S2 tide components. The current validation shows a good match with an average error of 10 cm/s and 8° in the speed major axis and its direction respectively between the simulation and the measurement. This proves the robustness and reliability of this model. It is also found that the cape effect is significant and important in this system. The dye diffusion simulations show a 53 d flushing period for the whole inner bay waterbody. The results are of its first kind for understanding the hydrodynamic system in the SCB and they can provide helpful and trustful scientific information for others. The Shacheng Bay (SCB) is one of the most complex coastal bays in southeast China and due to the fact of complicated geometry and dynamic coastal processes, it is considered as a challenging area for the numerical simulation of its hydrodynamic characteristics. The most advanced finite volume ocean model, finite-volume coastal ocean model (FVCOM), has adopted to simulate this hydrodynamic system, where tidal currents, tidal residual current and dye diffusion processes were studied and analyzed quantitatively. The validation of this numerical model matches well with various observations data, including elevation and current data. The misfit of a tidal elevation has a relative standard error of 3.66% and 4.67% for M2 and S2 tide components. The current validation shows a good match with an average error of 10 cm / s and 8 ° in the speed major axis and its direction respectively between the simulation and the measurement. This proves the robustness and reliability of this model. It is also fou nd that the cape effect is significant and important in this system. The results are its significant for important in this system. The dye diffusion simulations show a 53 d flushing period for the whole inner bay waterbody. The results are the first kind for understanding the hydrodynamic system in the SCB and they can provide helpful and trustful scientific information for others.