The invention discloses a boosting mechanism, in particular a boosting mechanism for a sealing device of a gas tank, belonging to the technical field of mechanical engineering. The boosting mechanism comprises a piston structure, a balance weight, a lever, two steel wires, a spring plate, a pressure lever, a rubber clamping device, a hanging mechanism, a cylinder body lateral plate, sealing oil, sealing rubber and canvas, wherein the joints of the steel wires and the steel wires are fixed by clamping the joints of the steel wires and the steel wires above the sealing oil by using steel wire clamps. The joints of the steel wires are moved to a position above a piston oil groove, on which the steel wire joints are easy to observe and maintain, and the steel wires are provided with a plurality of the steel wire clamps and can not completely fall below the piston oil groove after the steel wire clamps fall off, therefore, workers can maintain the steel wire above the piston oil groove. The invention thoroughly solves the problem that the production stop of the gas tank is caused by the falling-off of the steel wire clamps and can be extensively applied to sealing devices of thin oil sealing type gas tanks.