Abstract: Objective To explore the effect of hyperbaric oxygen therapy on the immune function of patients with severe craniocerebral trauma.Methods A total of 60 severe craniocerebral trauma patients were divided into two groups, and given different treatments. By FAC-SCalibur flow cytometry(Becton Dickinson Company U.S.) and immune turbidimetry, cell immunity and humoral immune function were determined and compared before and after treatment in the two groups of patients.Results Before treatment, the indexes of cellular immunity and humoral immunity showed no statistical difference between treatment group and control group(P>0.05). After treatment, T lymphocyte subsets and CD3, CD4 and CD4/CD8 ratio in treatment group was significantly higher than those in control group (P<0.01).Immunoglobulin IgG, complement C3 and C4 in treatment group was significantly higher than those in control group (P<0.01).Conclusion Hyperbaric oxygen therapy can improve the early immune function of patients with severe craniocerebral trauma, and is of an important significance in prevention of infection, reduction of complications, and improvement of cure rate and others.