The utility model discloses a water hydraulic pressure buoyancy adjustment system, the system include the casing, be filled with the gas of certain pressure in the casing, set up inner container, your bi -pass water hydraulic pressure magenetic exchange valve and double -acting water hydraulic pump in the casing the motor to is the inner container through foretell your bi -pass water hydraulic pressure magenetic exchange valve and double -acting water hydraulic pump the motor leads to so that carry out water transfer each other with the outer water environmental facies of casing, still set up and double -acting water hydraulic pump in the casing the motor that the motor is connected the generator, the control motor the control system of generator work with be used for storing the motor but the electric energy that the generator sent and the charging source for respectively installing the power supply in the casing. The utility model discloses a water hydraulic pressure buoyancy adjustment system and method, simple structure through dive and the come -up that the casing was adjusted to the quality that changes the inner container, realizes dive and come -up control to underwater operation equipment such as underwater robots.