The invention relates to a hydraulic valve cover manufacturing process. The process includes the following steps of a, discharging, wherein the required raw material is prepared according to weight and size, b, heating, wherein heating is conducted on the raw material in a heating furnace, c, upsetting, wherein the heated raw material is placed in an upsetting die, unsetting is conducted on the raw material to form a workblank, and the oxide skin on the surface of the workblank is removed; d, dummying, wherein performing is conducted on the workblank generated after the oxide skin is removed to form a pre-forging piece, e, precision forging, wherein fine machining is conducted on the preformed workblank to form a precision forging piece, f, burr cutting, wherein burrs of the precision forging piece are cut on a punching machine, g, normalizing, wherein the precision forging piece generated after burr cutting is conducted is placed in a furnace, and normalizing is conducted on the precision forging piece, h, shot blasting, wherein the oxide skin on the surface of the precision forging piece generated after normalizing is conducted is removed and i, cold sizing, wherein local cold sizing is conducted on the precision forging piece on a cold forging machine. According to the hydraulic valve cover manufacturing process, the workblank is formed through hot forging, then cold-extrusion is conducted on a key face, the plane degree and parallel degree are guaranteed, traditional machinery machining is replaced, the production cost is saved, and the forged piece is high in mechanical strength and stable in size accuracy.