Bijaw surgery should be bimaxillary surgery, not orthognathic surgery, with simultaneous maxillary and mandibular surgery. The indication is that the dentofacial deformity is the result of the simultaneous action of maxilla and mandible. The common bimaxillary protrusion is simultaneous maxillary and mandibular protrusion. Mandibular protrusion refers to overdevelopment of mandible and hypoplasia of maxilla. Therefore, in orthognathic surgery, both maxilla and mandible should be operated at the same time. During the operation, the mandible will be pushed backward and the maxilla will be pulled forward, which can change the anti-jaw relationship between the upper and lower jaws and form a normal mandibular coverage. There is also a micrognathia, that is, the mandible is seriously underdeveloped, which may be accompanied by overgrowth of the maxilla. Therefore, the operation needs to retract the maxilla and extend the mandible, so that the maxilla and mandible form a normal coverage relationship, not a deep coverage relationship.