OBJECTIVE： To investigate the effects of Dexmedetomidine hydrochloride injection on elderly patients underwent thoracic surgery during anesthesia recovery period. METHODS： Totally 60 elderly patients underwent thoracic surgery in our hospital during Jun. 2014-Feb. 2016 were selected as research objects and then divided into control group and observation group according to even and odd-numbered admission order， with 30 cases in each group. Control group was given Propofol injection 0.5-1 mg/kg intravenously 5 min after mask oxygen inhalation. Observation group was given Dexmedetomidine hydrochloride injection 0.5-1.0 μg/kg intravenously. Both group were successively given Etomidate emulsion injection 0.1-0.2 mg/kg， Sufentanil citrate injection 0.3 μg/kg and Cisatracurium besilate for injection 0.2 mg/kg intravenously for anesthesia induction； tracheal intubation was performed and ventilator was used to assist ventilation after anesthesia induction. And then control group was given continuous intravenous dripping of propofol 3-6 mg/kg·h； observation group was given continuous intravenous dripping of Dexmedetomidine hydrochloride injection 0.2-0.5 μg/（kg·h）. At the same time， both group were given continuous intravenous dripping of sufentanil 0.1-0.2 μg/（kg·min） and cis-atracurium 1.5-2 μg/（kg·min）， and continuously inhaled 1％-2％  sevoflurane for anesthesia maintenance. Hemodynamic index（HR，MAP，SpO2）， postoperative recovery， the occurrence of delirium， restlessness， cough and involuntary movement were observed in 2 groups before surgery （T0）， after anesthesia induction （T1）， at the moment of sputum suction and extubation （T2）， 5 min after extubation （T3）， 30 min after extubation （T4）. RESULTS： At T2 and T3， HR and MAP of control group were increased significantly compared to at T0， T1， and higher than those of observation group， with statistical significance （P＜0.05）. At T0， T1， T4， there was no statistical significance in HR and MAP between 2 groups （P＞0.05）. At T0， T1， T2， T3， T4， there was no statistical significance in SpO2 level between 2 groups （P＞0.05）. The breathing recovery time， eye openning time and extubation time of observation group were significantly shorter than those of control group， with statistical significance （P＜0.05）. The incidence of postoperative restlessness， delirium， cough and involuntary movement in observation group were significantly lower than control group， with statistical significance （P＜0.05）. CONCLUSIONS： Dexmedetomidine hydrochloride injection can keep hemodynamics stable in elderly patients underwent thoracic surgery during anesthesia recovery period.， shorten recovery time and reduce the occurrence of stress response as postoperative delirium， restlessness， cough， involuntary movement.