The movements of the upper jaw and the lower jaw could be predicted by model surgery in classic procedure of the treatment of asymmetric dental facial deformity. However, it is difficult to predict the position and the orientation of the chin after the maxilla and mandible osteotomy and reposition according to the model surgery. Therefore, it is impossible to make the decision whether genioplasty would be performed or not before the operation for the surgeon as well as the patient. Furthermore, if genioplasty were necessary, the movement of the chin could be made only according to the surgeon’s subjective judgement and his or her experience during the operation. The aim of this present study is to use computer assisted surgery to simulate the osteotomy and reposition of the maxilla and mandible, and then guide the genioplasty in the surgical treatment of asymmetric jaw deformities. The CT data of jaws were processed using Surgicase 5.0. The simulation of maxillary and mandibular osteotomy and reposition was performed according to the surgical plan based on the diagnosis, measurement as well as the results of model surgery. Then the position, shape, size and orientation of chin were evaluated after the maxilla and mandible asymmetry had been corrected in computer simulation. And whether the genioplasty should be performed were determined. Meanwhile, the osteotomy and reposition of the chin were simulated if the chin shifted to one side or there were any other asymmetric deformity. Totally, 120 cases of asymmetric dental facial deformity had been corrected with the guidance of computer assisted surgery. Therefore, with the guidance of computer assisted surgery, the necessity of genioplasty could be anticipated in the management of asymmetric jaw deformity. At the same time, the accuracy of the operation could also be improved based on the computer simulation.