Objective To study the efficacy of hyperbaric oxygen (HBO) therapy in improving scores of intelligence and emotion in patients with mild and moderate traumatic brain injury. Methods Sixty-seven patients with mild and moderate traumatic brain injury were randomly divided into HBO group ( n =34) and control group ( n =33). Both groups were given the basic therapy for closed brain injury. Besides, those in the HBO group were treated with HBO at the pressure of 0.18-0.22 MPa. The oxygen concentration in the cabin was controlled below 23% and oxygen uptake was 85 min/time and lasted for 100 minutes, once a day for three courses of ten times each. All the patients were evaluated with Mini-Mental State Examination (MMSE) - Chinese version, Self-rating Depression Scale (SDS) and Self-rating Anxiety Scale (SAS) before and after therapy. Results Before therapy, there was no obvious difference in the item scores or total score of MMSE, total score of SDS or total score of SAS between the two groups. All the scores after therapy were obviously better than those before therapy in both groups, and most scores after therapy were better in the HBO group than those in the control group ( P <0.05). Conclusions HBO therapy plays a significant role in improving scores of intelligence and emotion in patients with mild and moderate traumatic brain injury.