Objective To explore the feasibility of ultrasound-guided transverses abdominis plane block assisted with dexmedetomidine in the elderly patients underwent inguinal hernia repair and the influence on postoperative cognitive function. Methods 60 elderly patients undergoing unilateral inguinal hernia repair were randomly divided into 2 groups. Group Ⅰ was given 0.5 μg/kg dexmedetomidine by intravenous infusion for 10 min before ultrasound guided transverse abdominis plane block implement, followed by 0.4 μg·kg^-1·h^-1 intravenous infusion until 10 min before the end of operation. If anesthesia effect was not satisfactory or it failed, intravenous fentanyl 50～100 μg assisted anesthesia or general anesthesia with laryngeal mask would be used. Group Ⅱ was given intravenous combined inhalation general anesthesia with laryngeal mask. Postoperatively the patients were given controlled intravenous analgesia in both groups. Vital signs were observed for both groups during the operation. MAP and HR at skin incision, 30 min after incision and the end of operation were measured, and pain scores at 6, 12, 24 and 48 h after operation and the times of PCA during 48 h post-operation were compared between the two groups. All patients took the Mini-Mental State Examination(MMSE)neuropsychological tests before the operation and again two days after the operation. The numbers and the incidence of postoperative cognitive dysfunction(POCD)in both groups were calculated. Results In group Ⅰ HR slowed down during the operation though still in the safe range; anesthesia in 27 cases were satisfactory, while in 3 cases it was an incomplete block. There were no complications related to transverses abdominis plane block. The difference in Pain scores at 6, 12, 24 h after operation, the times of PCA during 48 h after operation and the incidence of POCD between two groups were significant. The difference in the scores of MMSE two days after operation were significant between two groups, and the scores were significantly lower than that before the operation in both groups. Conclusion For the elderly patients undergoing inguinal hernia repair, ultrasound-guided transverses abdominis plane block assisted with dexmedetomidine can provide a new anesthesia choice because of its ease of operation, good anesthesia effect and postoperative analgesia, especially the reduction of the frequency of POCD.