One-lung ventilation, lateral position and thoracotomy will bring a series of pathophysiologic changes that lead to pulmonary shunt and perioperative hypoxemia in the patients; meanwhile, the inhalation of anesthetics inhibits protective mechanism of hypoxic pulmonary vasoconstriction (HPV) in the lungs which further increases the incidence rates of hypoxemia and atelectasis. The patients will face significant problems of thoracotomyinduced lung ischemia-reperfusion injury and postoperative pain together with atelectasis. At present, thoracic epidural anesthesia combind with total intravenous anesthesia is an ideal anesthesia for thoracic surgery, Morphine is the main analgesic injected into the epidural space for postoperative analgesia, however, there are some deficiencies such as intraoperative awareness and postoperative insufficient analgesia. Dexmedetomidine is a new type of alpha-2 receptor agonist, its binding rate with alpha-2 receptor is 1,620 times higher than that with the alpha-1 receptor, it can selectively activate the central and peripheral alpha-2 adrenergic receptors. Dexmedetomidine has protective effect on the lungs, can effectively improve the self-protection mechanism (HPV) of the lungs to reduce hypoxemia, maitain the stability of circulation, inhibit the stress respones; and as a new adjuvant analgesic, improve postoperative analgesia. Dexmedetomidine has the effect of anterograde amnesia, and is effective in preventing intraoperative awareness combined with Propofol and improving postoperative cognitive function. To summarize the mechanism and advantages of Dexmedetomidine will be elaborate to investigate the perioperative anesthesia managements of thoracic surgery.