【Abstract】 Objective To observe the clinical effect of hyperbaric oxygen therapy(HBOT) and impact of the different start time of HBOT on the patients with diffuse axonal injury(DAI).Methods 84 patients with cognitive dysfunction DAI were divided into HBOT treatment group (42 cases) and conventional treatment group (42 cases). The clinical effect and prognosis was determined by Glasgow outcome score (GOS) and minimental state examination (MMSE) and activities of daily life (ADL) before and 6 months after the treatment in all the patients. 42 patients of HBOT treatment group were divided into group A (20 cases) and group B (22cases), according to the start time of HBOT. The clinical effect was observed and compared between the two groups. Results The rate of good prognosis in HBOT group (4762%, 20/42) was significantly higher than that in the conventional treatment group (1905%, 8/42) 6 months after the treatment (P＜005). There were significantly differences in MMSE and ADL scores before and 6 months after HBOT in HBOT group (P＜005). There were significantly differences in MMSE and ADL scores before and 6 months after the treatment in the conventional treatment group. There were significantly differences in MMSE and ADL scores 6 months after the treatment between both the HBOT and conventional treatment groups (P＜005).The MMSE and ADL scores in the A group were better than those of B group there were significant differences between the two groups (P＜005).ConclusionHBOT has important effect on treatment of diffuse axonal injury. It can obviously decrease mortality rate and improve prognosis. The earlier the treatment starts, the better the curative effect is when the hyperbaric oxygen therapy is applied to the patients with DAI.