The operation risk of mandibular angle hypertrophy correction is high, and the operation process is also complicated. There are three methods for the operation: intraoral, extraoral and combination of intraoral and extraoral. In the past, extraoral (incision behind the earlobe or lower edge of mandible) was used, which would leave postoperative scars. Therefore, intraoral incision has been adopted in recent years. The specific operation steps are as follows: 1. Preoperative design refers to the design of bone line, and the angle of mandibular angle is measured according to X-ray before operation. At present, computer-aided and rapid prototyping technology can be applied to make a solid model of mandible and design the range of mandible to be cut according to the model. Osteotomy methods include partial resection of mandibular angle, sagittal cleavage of outer plate, and partial masseter muscle resection. 2. Anesthesia: The operation is performed under general anesthesia or enhanced local anesthesia. 3. Incision and stripping: the incision is located at the bottom of buccal gingival sulcus in the mouth, stripping layer by layer to expose the mandibular angle. 4. Osteotomy: according to the designed bone line, the mandibular horn bone is cut off with a surgical saw, and then the osteotomy wound base is polished smoothly with a grinding head. Sagittal split resection of external plate includes mandibular angle osteotomy and external plate resection to reduce the distance between bilateral mandibles. 5. If the masseter muscle is hypertrophy, remove part of the masseter muscle. 6. Suture and pressure bandage, and place negative pressure drainage for 2-3 days if necessary.