Objective To determine the effect of moderate hypothermia on coagulation in patients with severe traumatic brain injury (sTBI) and investigate the clinical significance of thrombelastogram (TEG) monitoring.Methods Seventy-five patients with sTBI were randomly assigned to hypothermia group (conventional treatment + moderate hypothermia within 24 hours posttrauma,n =38) and control group (conventional treatment alone,n =38).TEG aided in monitoring coagulation function by measuring clot reaction time (R),clot formation time (K),clotting rate (α),maximal amplitude (MA),and percent fibrinolysis at 30 minutes after MA (LY30).Meantime,the intracranial pressure,vital signs,blood gas values,and blood electrolytes were also measured.Outcome was evaluated by using Glasgow outcome scale (GOS).Results The two groups were similar on admission with respect to R,K,α,MA,and LY30 (P>0.05),but the coagulation index in hypothermia group was significantly different from that in control group at days 1,2,3 and 7 posttreatment (P<0.05).Moreover,moderate hypothermia therapy demonstrated decrease of intraeranial pressure (P<0.01),with no severe complications,low mortality and improved outcome in comparison with control group.Conclusion Moderate hypothermia improves the hypercoagulability in patients with sTBI without increasing the risk of hyperfibrinolysis and protects brain tissue by decreasing intracranial pressure.