Objective To investigate the effect of hyperbaric oxygen (HBO) combined with external diaphragm pacing(EDP) in off-line treatment of patients of acute cervical spinal cord injury with respiratory failure. Methods A total of 50 patients with acute cervical spinal cord injury and semi-respiratory failure admitted to Mingzhou Rehabilitation Hospital of Nanchang from May 2019 to January 2022 were selected as the study subjects, and they were divided into the control group and the observation group according to random number table method, with 25 cases in each group.The control group was given conventional treatment, and the observation group was treated with HBO combined with EDP. Both groups were treated for 3 weeks. The off-line success rate, diaphragmatic mobility, lung function indexes(forced vital capacity [FVC], forced expiratory volume in one second [FEV1]) and mechanical ventilation time were compared between the two groups. Results The off-line success rate of the observation group was higher than that of the control group, and the difference was statistically significant (P＜0.05). There were no significant differences in the indexes of diaphragm movement and lung function between the two groups before treatment (P＞0.05). After treatment,the levels of diaphragm mobility, FVC and FEV1 in the observation group were higher than those in the control group,and the differences were statistically significant (P＜0.05). The mechanical ventilation time of the observation group was shorter than that of the control group, and the difference was statistically significant (P＜0.05). Conclusion HBO combined with EDP can improve the diaphragm mobility and lung function indexes of patients with acute cervical spinal cord injury and respiratory failure, effectively relieve respiratory failure, thereby increasing the success rate of weaning and shortening the mechanical ventilation time.