Abstract: The intermittency and randomness of the output power of the photovoltaic system are compensated by the energy storage of a supercapacitor bank to ensure smooth power supply of the ship power system. The characteristic of the supercapacitor and the structure of the photovoltaic system are studied and the model of the photovoltaic cell array and the MPPT（Maximum Power Point Tracking） control are built with the disturbance observation method. The power regulating device composed of a supercapacitor bank and a bidirectional DC/DC converter is constructed to absorb or compensate the sudden change of the power. The output power of the grid-connected inverter is controlled according to the control strategy of constant power. A test platform simulating irradiance adjustment is built. The effectiveness of the design is verified: the ultracapacitor in the marine grid-connected photovoltaic system can smooth the output power and can suppress the fluctuation of power grid frequency and phase voltage, improving the stability of the system.