Abstract: In order to meet the power supply needs of marine monitoring submersible systems,an underwater wave energy capture system with few components and a simple structure is developed and designed for use in submersible beacons,and the system is environmentally friendly in terms of the working mass compared to wave energy generation devices using hydraulic systems. The system consists of a liquid capsule,a main body,a foundation and an energy transfer system,using water as the working mass. The system was tested in a laboratory wave tank and found to be suitable for long periods and large wave heights,with a maximum power of 0.20 m,3.4 s and 5.2 W and a maximum efficiency of 0.08 m,3.1 s and 25%. The power and efficiency of the system decreases rapidly as the depth of the bladder increases,providing a reference for subsequent practical applications.