Abstract: Objective To study the effect of hyperbaric oxygen therapy on insomnia. Methods Seventy-four patients with insomnia but with no organic disease admitted to our hospital were randomly divided into control group and observation group.Patients in control group were routinely treated with drugs while patients in observation group received hyperbaric oxygen therapy. Results The total effective rate was 92.1% and 72.2% for the control group and observation group,respectively（P＜0.05）.No statistical difference was observed in average sleep time 1 and 6 months between the two groups after hyperbaric oxygen therapy（P＞0.05）. Conclusion The effect of hyperbaric oxygen therapy is better on insomnia than that of conventional therapy.