The utility model relates to an inflatable linear cylinder piston, which comprises a piston and a piston rod. The piston is characterized in that an annular groove is arranged on the inner side of the piston, an annular inflatable ring is arranged in the groove, an air nozzle is arranged on the inflatable ring, and a sealing cover is arranged on the air nozzle. The invention adjusts the pre-compression amount of the piston by the air pressure of the air-filled ring, so that the piston can still have good sealing effect after wearing and prolonging the service life of the piston; at the same time, the sealing cover on the air nozzle can slow down the air leakage speed of the air-filled ring.