Based on the anatomical studies, the authors had designed an operation for treating old dorsal subluxation of the inferior radio-ulnar joint.The periosteum was longitudinally incised at the dorsal side of the lower ulna. forming musculo-periosteal flap, and a periosteal flap, and a periosteal valves of pronator quadratus. They were subluxation, passing the flap from palmar to the dorsal side through thc subperiosteal tunnel at the lateral margin of the radius corresponding to the ulna. Then it was circled round the lower end on the ulna and sutured to the muscular flap and the tough interosseous membranes at the palmar side, being used to stabilize the recuperated dorsal subluxation of the inferior radio-ulnar joint. The result of its clinical use was satifying.