【Abstract】 Objective To investigate influence of dexmedetomidine on postoperative awakening and cognitive function in elderly patients undergoing endoscopic sinus surgery. Methods 60 elderly patients of selective endoscopic sinus surgery were selected in hospital from April to November in 2016 and randomly divided into experiment group (D group)and control group (C group)．In D group, the patients received intravenous injection of DEX (05ug/kg) before anesthesia induction，and then received continuous injection of DEX at a rate of 0205ug/kg/h till 30 min before the operation finishing．In C group, physiological saline was used instead of DEX. Mean arterial blood pressure (MAP) and heart rate (HR) were determined before anesthesia (T0), during intubation (T1)，1 hour after operation(T2)，during extubation (T3). The postoperative awaken time，agitation during awaken period，cognitive function and adverse reactions were observed. Results Changes of HR and MAP in D group had no obvious fluctuation. In C group，HR and MAP increased significantly at T1，T3. HR and MAP at T1，T2，T3 in D group were significantly lower than C group. Two groups of patients with spontaneous breathing recovery time, awake time and extubation time were no significant difference (P＞005). The incidence of agitation and SAS scores were significantly higher in C group than those in D group (P＜005). Sedation score in D group was significantly higher than that in C group (P＜005), there was no difference in MMSE score between the two groups before anesthesia induction (P＞ 005), and the degree of reduction in D group was more significant than that in C group.There was no significant difference in the incidence of adverse reactions between the two groups (667% vs 1333%) (P＞ 005), and there was no significant adverse reaction. Conclusion Using DEX in elderly patients of endoscopic sinus surgery, with preinjection 05ug/kg and continuous injection at a rate of 0205ug/kg/h till 30 min before the operation finishing, can effectively reduce hemodynamic fluctuations and reduce the incidence of agitation during recovery period and improve the safety of anesthesia,without the disadvantage of prolonging the recovery and extubation time.