The angular deformity of distal humerus is one of the most frequent complication of supracondylar fracture in growing children. The deformity rarely limits function, but corrected by patients request due to cosmetic problem. Many orthopedic surgeons have suggested various operation methods but with high incidence of complications related to these operations, also we often experience secondary deformity after inaccurate osteotomy. Therefore to identify desirable operative method to reduce secondary deformity, a retrospective study of 17 patients operated with angular deformity following distal humerus fracture was carried out in which replanning with isosceles triangle method was done in all cases. The following results were obtained. 1. The complications were two cases of metal failure and one of non union. 2. The basic requirement of closing wedge osteotomy without secondary deformity was that:the center line of isosceles triangle whose apex angle should be identical to the deformity angle and be placed on the concave apex of deformity, should overlap the transverse bisector of hurnerusforearm axes. In inevitable cases, the disparity should be minimized to alleviate secondary deformity. 3. The translation was calculated by the equation of T=Dxsin α(T:translation, D:proximal or distal migration of the point of contact of humerus-forearm axes, α:angle of the deformity). In conclusion, we think that the deformity may be corrected safely and easily using minute preoperative planning with application of above principle.