Abstract： Objective To observe the clinical effects of combined mild hypothermia and high dose of magnesium sulfate (MHMS) in treatment of diffuse axonal injury (DAI).Methods 64 patients suffered from DAI and had Glasgow Coma Scale (GCS) scores of 3 to 8.They were randomly divided into two groups: MHMS treatment group (n=32) and control group (n=32).MHMS treatment group: mild hypothermia was used to keep the rectal temperature at 33 to 35℃ and received 24 mmol magnesium sulfate intravenously at 20 minutes after admission,followed by 80 mmol magnesium sulfate intravenously everyday for 3 to 5 days.Control group: patients were only treated with common method without MHMS.Serum neuron specific enolase (NSE),GCS and GOS of all the patients were measured.GCS score was recorded at admission,at 3 days,7 days,and 2 weeks;serum NSE values was measured at admission,at 3 days and 7 days.Outcome was determined by Glasgow Outcome Scale (GOS) score at discharge and after 3 months.The data were analyzed statistically.Results The serum NSE,GCS and GOS in the MHMS group were (24.8±19.2)g/L,12.3±3.3 and 4.6±1.3,respectively;while in control group were (49.7±23.1) g/L,9.8±2.8 and 3.0±1.5,respectively.There was significant difference between the two groups in serum NSE,GCS and GOS (P＜0.01).Conclusion Mild hypothermia combined with high dose of magnesium sulfate therapy is effective in the treatment of patients with DAI.