The maximum energy capture and the stability of output power of marine current turbine can be achieved by storage methods based on hydraulic transmission system， which consists of an energy input system， a hydraulic pressure system， a generation system and a control system. A mathematical model of the system is established and computer simulation is done according to the model. Various working conditions are simulated on a semi-physical simulation platform. The computer and physical simulation results show that the variable speed constant frequency control of marine current turbine can be achieved， to maximize energy capture and stabilize power outputs.