Sealed hydraulic cylinder

The invention-creation provides a sealed hydraulic cylinder, which comprises a cylinder barrel, a piston and a piston rod, wherein the periphery of the piston is provided with a primary sealing groove and secondary sealing grooves; the secondary sealing grooves are arranged in the two ends of the primary sealing groove; a combinative sealing ring is arranged in the primary sealing groove; the combinative sealing ring comprises a matrix sealing ring, a compensating sealing member and a primary sealing member; the periphery of the matrix sealing ring is provided with a groove in a radial direction; the primary sealing member is arranged in the groove; the compensating sealing member is arranged between the matrix sealing ring and the piston; guiding layers are arranged in the secondary sealing grooves. When the sealing in a special size is required, the matrix sealing ring in a sealing member in a slightly large size is only needed to be turned, and then, is assembled with the compensating sealing member and th