Micromandibular deformity, also known as true short jaw deformity, can have both congenital, developmental disorder causes and acquired. Common congenital causes are genetic, such as Treacher-collins syndrome. Developmental micrognathia is commonly caused by childhood trauma, infection, or birth injury to the condyle that affects the development of the mandible. Acquired micromaxillary deformity can be seen after traumatic fracture dislocation healing, tumor resection, etc. Micromandibular deformity not only affects the aesthetics, but also is accompanied by disorder of the occlusal-dental relationship, snoring and other symptoms of airway obstruction. Usually after lengthening surgery, orthodontic treatment is performed after 3-6 months of fixation to correct the abnormal occlusal relationship. We usually take mandibular lengthening combined with orthodontic treatment immediately after lengthening to obtain good results in the treatment of micromaxillary deformity.