The practical diagnosis, plan of treatment and procedure of the mandibular prognathism is summarized in this article. The treatment for such parients is placed under the category of the plastic surgery. Recently the orthodontic surgery have been growing in our clinic because of the increase of the cosmetic desire of the patients, which is caused by the medical development of the plastic surgery and his social and economic stability. As we need to make a maximum effort for a patient to be satisfied, we must establish the criteria of the diagnosis and the plan of the treatment of such patients. Moreover, we must cooperate the orthodontist and the prosthesist closely to produce for him a good occulusion an a good health.