Abstract: Objective To study the influence of dexmedetomidine on stress response and early cognitive function of elderly patients after spinal operation. Methods A total of 66 elderly patients undergoing spinal surgery in our hospital between February,2015 and September,2016 were enrolled and randomly divided into dexmedetomidine group (observation group) and saline group (control group) with 33 patients in each group.All patients were given same anesthesia induction and intraoperative anesthesia maintenance with same drugs and doses,but patients in the observation group were given dexmedetomidine with loading dose 0.5 μg/kg before anesthesia induction,after 15 min continuous infusion,and then at the speed of 0.3 μg/(kg·h) until 30 min before the end of surgery.The stress related index such as serum cortiso (Cor),Angiotensin Ⅱ(Ang Ⅱ),epinephrine (E),norepinephrine (NE) levels,and the cognitive function related index such as S-100β protein (S-100β),serum tumor necrosis factor-α(TNF-α) and interleukin-6(IL-6) levels were tested by ELISA;The Mini Mental State Examination (MMSE) was used to systematically assess the incidence of postoperative cognitive dysfunction (POCD). Results Cor level in the control group at 1,4,8 and 12 hours after surgery increased significantly as compared with that 10 min before anesthesia,which was significantly higher than those in the observation group (P<0.05);The levels of Ang Ⅱ,NE and E at 1,4,8,12 and 24 hours after the surgery all decreased significantly as compared with those 10 min before the anesthesia,and they were lower than those of control group with statistical significance (P<0.05);the levels of S-100β,TNF-α and IL-6 at 1,3 and 5 days after the surgery in the control observation group were significantly higher than those 1 day before the surgery (P<0.05),and they were all higher than those of observation group with statistical significance (P<0.05);The MMSE score at 1,3 and 5 days after the surgery in the control group was much lower than those 1 day before the surgery (P<0.05),and they were all lower than those of observation group with statistical significance (P<0.05);The incidence of POCD at 1 and 3 days after the surgery in the observation group were lower than control group with statistical significance (P<0.05). Conclusion The application of dexmedetomidine in elderly patients with spinal surgery can reduce the stress response in 24 hour and the incidence of early postoperative cognitive dysfunction.