Objective To investigate effects of very early hyperbaric oxygen treatment (HBOT) on patients with malignant brain edema after surgical operation for treatment of severe traumatic brain injury (TBI).Methods A total of 146 patients who suffered from malignant brain edema after last surgical operation for severe TBI were enrolled for this study.According to the intervention time of HBOT,they were randomized into a very early group (HBOT within 3 days after operation,n =55),an ordinary group (HBOT at 4 to 10 days after operation,n =65) and a control group (non-HBOT,n =26).Mortality rate of the 3 groups were recorded within 4 weeks after operation,and GCS (Glasgow Coma Scale) score were assessed in 1,2,3 and 4 weeks after operation.Dynamic head CT scan were performed for detecting brain status and for determine the duration of brain edema.Results The mortality of the very early group,the ordinary group and the control group were 10.9％,7.7％ and 11.5％,respectively,and no statistically significant difference was revealed among the groups (P ＞ 0.05).In very early group,the GCS scores of 1,2,3 and 4 weeks after operation were (8.837 ±3.350),(10.755 ± 3.388),(11.633 ± 3.408) and (12.367 ± 3.408),respectively,with significant difference between the time points 1 week and 2,3 and 4 weeks as well as 2 and 4 weeks after surgery (P ＜0.05),but not between 2 and 3 as well as 3 and 4 weeks after surgery (P ＞ 0.05).In ordinary group,the GCS scores at 1,2,3 and 4 weeks after surgery were (8.509 ±3.042),(9.458 ±3.115),(10.186 ±3.203) and (10.627 ±3.439),respectively,with significant difference between 1 week and 2,3 and 4 weeks after operation (P ＜ 0.05).In control group,the GCS scores at 1,2,3 and4 weeks after surgery were (8.042 ±2.881),(8.417 ±2.962),(8.542 ±3.02) and (8.958 ± 3.043),with no statistical difference among different time points (P ＞ 0.05).When compared with the very early group,the GCS sores of the ordinary group and the control group were significantly lower after intervention (P ＜ 0.05),and the GCS of control group was lower than that of the ordinary group (P ＜ 0.05).As for brain edema duration,the very early group was the shortest among the 3 groups (P ＞ 0.05) Conclusion Very early hyperbaric oxygen treatment could improve consciousness state and alleviate malignant brain edema after surgical operation in TBI patients.