Abstract： Objective To investigate the effect of hyperbaric oxygen on high mobility group protein B1 (HMGB1) expression in the tissues of spinal cord injury,and the characteristic of secondary inflammatory response after spinal cord injury.Methods According to the randomization table,160 healthy and adult Sprague-Dawley (SD) rats were equally divided into 4 groups,including the spinal cord injury group,the spinal cord injury + hyperbaric oxygen group,the sham operation group and the sham operation + hyperbaric oxygen group.Each group was further randomly and equally divided into 4 subgroups:the 1st,3rd,7th,14th day groups.BBB score was used to evaluate functional rehabilitation of indlimb and the methods of PCR,Western blot,immunohistochemistry were performmed to determine the expressions of HMGB1 and nuclear factor kappa B (NF-κB) in the damaged tissues at different time points after spinal cord injury.Results The levels of mRNA and the expressions of protein of HMGB1 and NF-κB in the damaged tissues after spinal cord injury were significantly increased (P ＜0.01 ).By pre and posthyperbaric oxygen intervention,No significant differences the level of HMGB1 mRNA and the expression of HMGB1 protein after spinal cord injury (P ＞0.05) on the 1st and 3rd days,but there were significant differences on the 7th and 14th days (P ＜ 0.05 ).Hyperbaric oxygen intervention reduced the level of NF-κB mRNA and NF-κB protein expression,without significant difference (P＞0.05) on the 1st day,with significant differences (P ＜0.05) on the 3rd,7th and 14th days.After hyperbaric oxygen intervention,the BBB scores were significantly higher on the 7 th and 14th days (P ＜ 0.05).Conclusions Hyperbaric oxygen can reduce secondary inflammatory response after spinal cord injury by restricting the expression of HMGB1 and promoting the repair of neurological function.