The invention relates to the field of buoyancy regulation design of a novel marine underwater vehicle, and provides a symmetric piston cylinder buoyancy regulation device. The device is composed of a control element, a power element, a transition element, an execution element, a sealing element, a fixed connection element and a protection element. According to the buoyancy regulation device, the movement of the underground vehicle in the depth direction of liquid is regulated according to the relative magnitude of buoyancy and gravity of the marine underground vehicle, and the symmetric piston cylinder buoyancy regulation device overcomes the defect that due to a single-cylinder piston structure, a piston rod connecting piece is easy to bend and influences smooth operation of a driving part lead screw and a lead screw nut. A motor drives the lead screw to rotate to drive a symmetric connection rod to move relative to the lead screw in the axial direction of the lead screw, and axial, radial and angular displacement generated during actual machining and assembling of a piston rod and a hydraulic cylinder is adjusted through a straight rod bulb-shaped knuckle bearing. The symmetric piston cylinder buoyancy regulation device has the advantages of being smooth in operation, simple in structure, low in cost and the like, enriches the type of the buoyancy regulation device of the marine underwater vehicle, and is remarkable in effect.