Abstract: Objective To analyze the effect of dexmedetomidin on hepatic ischemia-reperfusion injury in left hemihepatectomy. Methods Clinical data about 60 patients who underwent left hemihepatectomy in the First Affiliated Hospital of Chinese PLA General Hospital from January 2016 to December 2017 were analyzed. Patients were randomly divided into experimental group and control group. The experimental group were injected with dexmedetomidine at 1μg/(kg·h) before anesthesia and lasted for 10 minutes. Then dexmedetomidine were injected at 0.5 μg/(kg ·h) until the end of the operation. The patients in the control group were injected with the same dosage of saline. The liver function and cytokines were compared between two groups at T0 (before hepatic portal occlusion), T1 (after hepatic portal opening), T2 (before abdominal incision closure) and T3 (first day after operation). Results All patients received the surgery successfully. The operating time was (243.6±59.1) min, and the hepatic portal occlusion time was (24.7±10.3) min in experimental group. After the occlusion of the hepatic portal, the indexes of liver function and IL-6, IL-10, MDA increased gradually compared with baseline, and the SOD decreased gradually (all P< 0.05). At 1 day after operation, ALT, AST, ALP and TB in experimental group were significantly lower than those in control group ALT, (114.5±32.8) U/L vs (189.2±57.3) U/L; AST, (98.5±35.4) U/L vs (168.8±45.3) U/L; ALP, (206.5±78.3) U/L vs (297.7±116.4) U/L; TB, (20.8±6.2) μmol/L vs (24.9±8.3) μmol/L; all P< 0.05, IL-6 and MDA of experimental group were (176.5±28.7) pg/ml and (8.6±3.3) nmol/L, which were significantly lower than that of control group (276.5±74.2) pg/ml and (15.4±5.3) nmol/L (P< 0.05, respectively). However, the IL-10 and SOD of experimental group were significantly higher than those of control group (15.8±3.1) pg/ml vs (9.2±3.4) pg/ml, (37.6±10.1) U/ml vs (24.9±7.8) U/ml, P< 0.05, respectively. Conclusion Dexme-detomidine can inhibit the formation of oxygen free radicals and reduce the production of proinflammatory cytokines, which can protect the liver function from ischemiareperfusion injury.