The invention discloses an automatic turning device for a hydraulic control wire rope leg and relates to the automatic turning problem of the leg oil cylinder of a lorry-mounted crane; the invention aims at overcoming the deficiency of the prior art and provides a device which takes the turning oil cylinder of the lorry-mounted crane as a driving force and leads the leg oil cylinder to achieve automatic continuous turning within the scope of vertical 180 degrees; the invention adopts a technical proposal as follows: a manual pull beam is externally hinged with a leg frame by a fixed pulley shaft; the upper end of the leg frame is inversely provided with a leg oil cylinder and a turning oil cylinder; the middle part of the leg frame is provided with an idler wheel; the middle of the manualpull beam is provided with a wedge-shaped sheath which is arranged at the bottom right of the fixed pulley shaft; one end of the wire rope is fixed on the wedge-shaped sheath and the other end of thewire rope is fixed at the telescopic end of the turning oil cylinder; the middle part of the wire rope is wound on the idler wheel and the fixed pulley shaft; and the invention can be widely applied to the lorry-mounted crane.