The invention provides a piston sealing ring of a hydraulic motor. The piston sealing ring of the hydraulic motor comprises an O-shaped ring and a sealing ring, wherein an arc-shaped groove matched with the O-shaped ring is formed at the inner side of the sealing ring; an arc-shaped oil storage tank is arranged at the outer side of the sealing ring; and arc-shaped bulges are formed at the two sides of the arc-shaped oil storage tank of the sealing ring. The piston sealing ring of the hydraulic motor comprises the O-shaped ring and the sealing ring; lubricating oil can be placed in the arc-shaped oil storage tank; the working temperature is effectively reduced; the noise reduction effect is good; and the arc-shaped bulges are in contact with the inner wall of an outer cylinder, so that thepiston sealing ring of the hydraulic motor has a good sealing property and stable overall structure and is convenient to realize.