Objective:To evaluate the relationship between the occipitocervical angle(basilar vertebral angle [O-C 2 angle], mento-pharyngeal angle [M-P angle], and cervical range of motion [CROM]) and difficult airway after occipitocervical fusion surgery in the patients. Methods:This was a retrospective study. The clinical data from patients who underwent occipitocervical fusion surgery at our hospital from March 2018 to March 2023 were retrospectively collected. Preoperative and last follow-up airway assessment data and cervical lateral X-rays were collected to measure the O-C 2 angle, M-P angle and CROM. Patients were divided into negative group (Mallampati grade Ⅰ or Ⅱ, suggesting no difficulty in intubation) and positive group (Mallampati grade Ⅲ or Ⅳ, suggesting possible difficulty in intubation) based on the last follow-up modified Mallampati classification. Results:A total of 53 patients were finally included, with 18 cases in positive group and 35 in negative group. There were no statistically significant differences in the O-C 2 angle and CROM between preoperative and last follow-up in the 53 patients ( P>0.05), and the M-P angle was significantly decreased at the last follow-up compared with that before operation ( P<0.05). Compared with negative group, O-C 2 angle and M-P angle were significantly decreased at the last follow-up ( P<0.05), and no significant change was found in CROM in positive group ( P<0.05). Compared with that before operation, the M-P angle was significantly decreased at the last follow-up in both groups, and the O-C 2 angle was significantly decreased at the last follow-up in positive group ( P<0.05). The areas under the receiver operating characteristic curves of O-C 2 angle, M-P angle and CROM in predicting difficult airway were 0.895, 0.888 and 0.519 respectively. Conclusions:The decrease in the O-C 2 angle and M-P angle after occipitocervical fusion surgery can increase the risk of difficult airway, and both can be used for airway assessment in the patients undergoing this kind of surgery.