According to the need of underwater measurement equipment automatic recycling application, this paper introduces a design of electronic control buoyancy mechanism based on microprocessor. This mechanism takes the TI company's low power consumption microprocessor MSP430F149 as the core, the Intersema MS5541C pressure sensor as the sensing unit, the pneumatic solenoid valve as the controlled unit and takes the method of capacitor stored energy and release to drive the pneumatic solenoid valve and detects the maintain current to feedback regulate it . According to the demand of different condition of underwater measurement equipment to rise and descend, the buoyancy mechanism can control the pneumatic solenoid valve to close and release for adjusting the state of floating gasbag. This buoyancy mechanism has the advantages of high reliability and low power consumption.