Objective To study the biomechanics of osteotomy surgery for mandibular angle hypertrophy with drilling method and to explore the optimization and improvement of this operation. Methods Using the finite element method, the three-dimensional finite element models of osteotomy surgery for mandibular angle hypertrophy with drilling method as well as its modified operations are established,meanwhile, the stress analysis and comparison are performed. Results Model-1 (mandibular angle osteotomy surgery model by drilling method) had the highest fracture failure load among all surgical methods, which was 2426N. The failure loads of the other modified surgical models (model-2 ~7) were all lower than that of model-1, which were 2018N, 1854N, 1447N, 1183N, 1028N and 876N, respectively. Meanwhile, compared with other models, the stress distribution region of model-7 was the smallest, with the von Mises stress in operating side of the articular disc was greater than that of the non-operating side, and most of the area was between 0.52～3.25MPa and the maximum of 9.86MPa. Conclusion The non-uniform drilling and removal of the buccal cortical bone of the mandibular angle are combined with the maximum occlusal force and the constraint of the posterior margin of the mandibular ramus is the best operation method.