Telescopic oil cylinder of petroleum drilling machine

The utility model relates to a telescopic oil cylinder of a petroleum drilling machine. Comprising a telescopic assembly, the telescopic assembly comprises an oil cylinder shell, a sealing sleeve is arranged at the front end of the oil cylinder shell, a blanking cap is arranged at the tail end of the oil cylinder shell, a piston rod is slidably connected into the oil cylinder shell, and a piston block slidably and hermetically connected with the inner wall of the oil cylinder shell is arranged at the tail end of the piston rod; the auxiliary supporting assembly comprises a front end supporting ring embedded in the inner wall of the front end of the oil cylinder shell and a rear end supporting ring embedded in the inner wall of the rear end of the oil cylinder shell; the auxiliary supporting assembly further comprises a supporting shell coaxially arranged on the outer side of the oil cylinder shell, a plurality of sealing pins penetrating through the oil cylinder shell are arranged at the two axial ends of the