The metacarpal shaft fracture has been reported as a stable fracture relatively, but operative treatment is indicated when there happens reduction loss, or is in need of early exercise. Intramedullary K-wire fixation has been used for unstable transverse or long oblique diaphyseal fracture of the metacarpal bone. The fracture site is not opened and the K-wires are introduced under X-ray control. The techniques can stablize the fracture site and allow immediate exercise postoperatively. We experienced 9 cases of 4th metacarpal shaft fracture treated by percutaneous intramedullary K-wire frxation with modified technique. The K-wire was used one or two ezch metacarpal fracture. The types of fracture were 4cases of transverse, 3 of oblique, 2 of comminuted. The average clinical union period were 5 weeks. There were not severe complications in all cases.