To evaluate the effects of dexmedetomidine on tourniquet induced limb ischemia-reperfusion injury under general anesthesia . Sixty ASA I or II patients, scheduled for lower limb operation with tourniquet, were randomly divided into dexmedetomidine group (group D, n = 30) and control group (group C, n = 30). Combined general anesthesia was performed in both groups. In the group D, a dexmedetomidine intravenous infusion was started immediately after the femoral vein at a dose of0.1μg/kg/m for 10 minutes, followed by 0.7 μg/kg•h until the end of the operation, whereas group C received an equivalent volume of normal saline. Femoral venous and arterial blood samples were obtained at four time points: before operation started(T0), 1 min before tourniquet inflation (T1), 5 min (T2) and 20 min (T3) after tourniquet release. serum malondialdehyde (MDA)concentration, the total antioxidant capacity (TAC) concentration and artery blood gas analysis were measured. Results: There were no significant differences in serum MDA and TAC level before tourniquet inflation between two groups (P > 0.05). Serum MDA levels in group D were significantly lower than those in group C at T2-T4,respectively (P<0.05). Serum TAC concentration in group D was significantly higher than that in group C at T2-T3, respectively (P < 0.05). between two groups at all time points.Conclusion: Dexmedetomidine has protective effects on tourniquet-induced ischemia reperfusion injury in limb surgery, which may be due to dexmedetomidine reducing inflammatory cytokines levels and MDA concentration and increasing TAC concentration.