Objective: To investigate the effects of dexmedetomidine on postoperative cognitive function, hemodynamics and stress response in patients undergoing laparoscopic gynecological surgery. Methods: 150 cases of gynecological laparoscopic surgery in our hospital from March 2016 to May 2018 were selected as the study object, they were divided into three groups according to random number table method. dexmedetomidine was infused at a rate of 0.8 μg kg-1 h-1 in group A, dexmedetomidine was infused at a rate of 0.4 μg kg-1 h-1 in group B after anesthesia induction, while patients in the group C was given the same amount of normal saline. The hemodynamic changes, stress indicator, anaesthesia recovery time, pneumoperitoneum time, extubation time, residence time of PACU, improved sedation - agitation score (RASS) were compared among the three groups at different time points. The the occurrence of postoperative cognitive dysfunction (POCD) in the patients were recorded. Results: At T0(10 minutes before anesthesia induction), there were no significant differences in HR and MAP in the three groups (P>0.05). At T1 (1 min after tracheal intubation) and T2 (5min after pneumoperitoneum), HR and MAP in group A and group B were lower than those in group C, while HR and MAP in group A were lower than those in group B (P<0.05). At T3(end of surgery), HR in group A and group B were lower than that in group C (P<0.05). There were no significant differences in group A, group B and group C (P>0.05). The RASS score of group A and group B at 1 h, 6 h and 12 h after surgery were lower than that of group C (P<0.05), while that of group A at 1h, 6h and 12h after surgery was lower than that of group B (P<0.05). At T1, T2 and T3, the levels of Norepinephrine(NA) and Adrenocorticotropic hormone(ACTH) in group A and group B were lower than those in group C, while those in group A were lower than those in group B (P<0.05). The incidence of postoperative POCD in group A, group B, group C were 2.00% (1/50), 10.00% (5/50), 24.00% (12/50) respectively, the incidence of POCD in group A was lower than that in group C (P<0.05). There was no significant difference in the recovery time of anesthesia and pneumoperitoneum in the three groups (P>0.05). Conclusions: The perioperative application of dexmedetomidine in gynecological laparoscopic surgery is conducive to maintaining hemodynamic stability, reducing stress response and reducing the incidence of postoperative cognitive dysfunction, of which the effect of 0.8 μg kg-1 h-1 dexmedetomidine is more obvious. [ABSTRACT FROM AUTHOR]