Abstract: Large ocean buoys are needed to have the abilities of working independently, monitoring continuously and transmitting data in real time and a stable and convenient power supply system is the key to ensuring the normal operation of the buoy. The hybrid power supply system composed of solar energy and storage battery and widely used in the present is not only affected greatly by the alternation of day and night, the length of sunshine and the high salt and humidity sea environment, but also needs a high maintenance costs. As a kind of clean energy source and meanwhile having the character of uninterrupted energy acquisition, the wave energy can provide continuous power supply to the buoys. Thus, a large ocean buoy power supply system based on the principle of oscillating water column is designed, and the aerodynamic performance of the device is studied under different structural forms through numerical simulation. The calculation results show that the device has an optimal ratio of power to capture width when the ratio of wave length to gas chamber diameter L_d=5.5, the ration of orifice area to plate area e=1.25% and the ratio of wave length to gas chamber spacing L_k=7. By the structural optimization of the basic dimensions of the device, the ratio of power to capture width can be increased from 0.178 m⁻¹ to 0.260 m⁻¹, being enhanced by about 46.1%.