Tidal stream offers divinable and regular electricity generation at higher power densities than other renewable energy sources. With an increasing concern over the potential of harnessing ocean energy for electricity generation by marine current turbine (MCT) and its impact on water environment, the exploration and assessment works are required. Based on a three-dimensional ocean model with a developed marine current turbine submodel, we assessed the impacts of MCT on water environment and discussed the effect of MCT assignment on potential power extraction. The simulation results indicated that the reduction of water current velocity occurred at the installation area of MCTs. A certain amount of MCTs installed vertically to the water flow could achieve full utilization of marine renewable energy. However, more scenario simulations for MCT in different assignments should be conducted for the optimal design of MCT installation to further improve the utilization efficiency of marine renewable energy. Meanwhile, an ecosystem model would be combined with a hydrodynamic model to predict the impacts of MCT on the ecosystem.