[Objective] To introduce the surgical technique of one-stage flush osteotomy by combined anteroposterior approach for the treatment of congenital cervical hemivertebra deformity. [Methods] One case of congenital C6 hemivertebra deformity was treated by one-stage flush osteotomy by combined anteroposterior approach. In this patient, the vertebral artery passed through the transverse foramen of the right C6 hemivertebra. Part of the vertebral bodies of C6 and C7 were removed by anterior-posterior-anterior approach, so that the lower parts of C6 and C7 were aligned without management of the right vertebral artery of C6, and posterior C5-T1 pedicle screws and anterior plate fixation were used for correction. [Results] The operation was successful without complications such as spinal nerve injury and vertebral artery injury. The operation time was 5 hours, and the intraoperative blood loss was about 400ml. The torticollis improved significantly after operation, and the Cobb Angle of the cervical spine improved from 33° preoperatively to 5° postoperatively. Postoperative X-ray and CT showed good coronal balance of cervical spine and satisfactory internal fixation. [Conclusion] One-stage flush osteotomy by combined anteroposterior approach for the treatment of congenital cervical hemivertebra deformity is effective, especially the hemivertebra involves vertebral artery, while the adjacent lower vertebral body does not involve vertebral artery. This technique can avoid the treatment of vertebral artery during osteotomy and improve the safety of surgery.