Objective To illustrate the morphological changes of mandible after angle-splitting ostectomy. Methods From January 2006 to April 2008, 10 cases had undergone mandibular angle-splitting ostectomy to reduce the width of the lower face. For each patient, CT datum of mandible at three stages (preoperative, immediate postoperative, 6 months postoperative) were collected. By the application software of reverse engineering (Surfacer V9) and true-up and dissection techniques based on three-dimensional spiral computed tomography(3D-CT), operative efficacy and bone regeneration at the operation area of angle-splitting ostectomy were evaluated 6 months postoperative. Results 1)Concavity could be seen at the angle-splitting ostectomy area 6 months postoperative, especially at the mandibular external oblique line region. Average cup depth was (3.64±1.67)mm by contrasted to preoperative. Diminution of bone volume was 55%±9% for the local operative area 6 months postoperative. 2)Bone regeneration could be seen at the area that mandibular outer cortex had been removed. Compared with immediate postoperative, ratio of neoformative bone was 84.6% ±7.3% 6 months postoperative. The main region of bone regeneration was mandibular angle. Conclusion Mandibular angle-splitting ostectomy is an effective technique for reducing the width of the lower face. Masseter muscular movement should be restricted postoperative to prevent hyperostosis at the angle area.