The step seal is composed of a rubber O-ring and a polytetrafluoroethylene ring. The material is PTFE + NBR. In special cases, the rubber elastomer nitrile rubber NBR uses fluorine rubber FKM. It can be divided into step seal for hole and grid ring for shaft, but its sealing effect is the same. According to its own deformation, it will produce higher initial contact stress on the sealing surface and prevent the leakage of pressureless liquid. When the hydraulic cylinder is working, the pressure liquid passes through the elastic deformation of the O-shaped sealing ring to squeeze the square sealing ring to the greatest extent, making it close to the sealing surface, which produces a higher additional contact stress that increases with the pressure of the pressure liquid. Together with the initial contact stress, the leakage of pressure liquid is prevented.