A
buoyancy adjustment device for an
underwater vehicle, comprising a pressure-resistant cabin body, an
assembly part is arranged on the outer side of the pressure-resistant cabin body, and an air bag and a liquid bag are installed on the
assembly part; a
hydraulic control unit, a pneumatic
control unit and an
oil tank are installed in the pressure-resistant cabin body; the
hydraulic control unit is respectively communicated with the liquid bag and the
oil tank to enable the oil liquid to flow between the liquid bag and the
oil tank; the pneumatic
control unit is respectively communicated with the air bag and the pressure-resistant cabin body to enable the gas to flow between the air bag and the pressure-resistant cabin body; the outer periphery of the liquid bag and the outer periphery of the air bag are both fixed on the
assembly part, and the liquid bag wraps the air bag, so as to form a pneumatic cabin located between the air bag and the assembly part and a hydraulic cabin located between the air bag and the liquid bag. In the embodiment of the present invention, by arranging the air bag and the liquid bag, the form of
buoyancy adjustment is more diversified, and compared with sucking and discharging
seawater to change the self-weight, the
energy consumption is less, there is no limitation, and the
buoyancy can be adjusted larger or smaller; the air bag is nested in the liquid bag, which can reduce the occupation of the installation space and can be quickly emptied.