The purpose of this study was to determine the changes in hard tissues, soft tissues, and teeth after bilateral sagittal split ramus osteotomy and orthodontic treatment for the treatment of mandibular protrusion. Cephalometric analysis was used to evaluate the aesthetic effects and occlusal relationships obtained. The subjects included 11 women and 9 men (aged 18–27 years; average, 20 years) with mandibular protrusion who underwent bilateral sagittal split ramus osteotomy. Based on a preoperative computer-aided manufacturing/design-assisted, model surgical design and an occlusal guide plate, new occlusal relationships were established for the patients. In addition, the preoperative and the end of postoperative orthodontic treatment cephalometric radiographs were systematically analyzed. In all patients, the surgical incisions underwent primary healing, with no infection or osteonecrosis. Significant differences were observed in the preoperative and the end of postoperative orthodontic treatment values of all hard tissue and teeth parameters, except for SNA°, ANB°, GoGn-SN°, SE (mm), NP-FH°, SGn-FH°, OP-FH°, 1−-MP°, Li-E (mm). The most obvious significant differences were seen in SNB°, SND°, 1_-NA°, 1_-NA (mm), 1−-NB (mm), 1−-NB°, Po-NB (mm), NA-PA°, AB-NP°, 1−-OP°, Ui-E (mm), and S-N’-B’° (P < 0.001). Postoperative follow-up lasted for 10 to 12 months. All patients eventually achieved normal downjaw relationship, tooth arch forms, and spee curves. There were no evident irregularities of teeth arrangement or abnormal occlusal relationships were observed. All patients were satisfied with their facial appearance and occlusal relationships at the end of postoperative orthodontic treatment. The authors found a precise preoperative model surgical design combined with postoperative orthodontic treatment is a simple and time-saving technique. It can be used to correct mandibular protrusion with satisfactory occlusal relationship, facial appearance, and minimal postoperative complications.