Among the asymmetry of forehead and face development, 1/3 is the most common, and bilateral mandibular asymmetry is more common. Asymmetric parts can be confined to condyle or condyle neck, and can also include the whole mandibular branch or mandibular body, and can also involve the whole mandible. The clinical manifestations are that the affected mandibular condyle or condyle neck is too long, the mandibular angle is round and extends downward, the mandibular angle and chin are inclined to one side, the occlusal relationship is disordered, the midline of mandibular teeth is inclined to the healthy side, and some and all teeth on the healthy side are inverted (occlusal) or opposite (occlusal). The back teeth can be opened (occluded). Some patients have abnormal mandibular development on one side, which can affect the development of other facial bones and soft tissues, such as the inclination of eye plane and jaw plane, asymmetry of bilateral maxilla and even zygomatic arch, and inconsistent fullness of soft tissues on both sides. Surgery is the only way to correct it.