The invention discloses a roller weldment hydraulic positioning and rotating device. The roller weldment hydraulic positioning and rotating device comprises a power control device and a hydraulic positioning device, wherein the power control device comprises a base (6), a rotating control device (3), a rotating cable (13), a rotating motor (12), a hydraulic motor (11), a hydraulic cable (10), a hydraulic pump (9), a hydraulic oil supply pipe (8), a hydraulic oil tank (7), a hydraulic oil inlet pipe (15) and a hydraulic oil return pipe (5); the hydraulic positioning device comprises an arc grooved rail (14), a rotating wheel (4), a rotating wheel positioning pin (16), a positioning supporting platform (2), a positioning turnplate (1), a positioning groove (18), a hydraulic control valve (17), a roller positioning pin (20), a hydraulic piston rod (22) and a hydraulic cylinder barrel (21). The roller weldment hydraulic positioning and rotating device is simple in structure, convenient to use, low in cost, easy to popularize, and capable of effectively improving controllability of welding operation, positioning accuracy and welding-joint quality of rollers.