Objective To investigate the method, clinical effect, and complications of transoral odontoidectomy combined with posterior occipitocervical fusion in the treatment of basilar impression malformation.Methods A retrospective analysis was performed for the clinical data of 12 patients with compression of the medulla oblongata and the ventral upper cervical cord by the odontoid process who were treated in Department of Neurosurgery in The Second Affiliated Hospital of Kunming Medical University from September 2012 to May 2017. Among these patients, one had simple basilar invagination, 7 had basilar invagination with Chiari malformation, and 4 had basilar invagination with atlanto-occipital fusion. Transoral odontoidectomy combined with posterior occipitocervical fusion was performed for all patients. The patients were followed up for a long time after surgery and a statistical analysis was performed for imaging parameters.Results After a follow-up of 6 months to 2 years, 8 patients achieved marked remission, 3 had no change in abnormal sensation of the limbs, and 1 experienced cerebrospinal fluid leak two months later and was cured by repair and transfer of skin flap. No patient experienced wound infection. The changes in imaging parameters, including Chamberlain line, McGregor line, Webster line, Klaus height index, medullocervical angle, and cranial base angle, after surgery were measured; a statistical analysis was performed for such imaging parameters, and the results indicated statistical significance (P<0.01).Conclusions Transoral odontoidectomy is a direct and effective surgical method for compression of the medulla oblongata and the ventral upper cervical cord by the odontoid process. Adequate grinding of the odontoid process and necessary fixation can promote healing of patients and improve their quality of life.