Objective To investigate the effect of dexmedetomidine on perioperative anxiety of patients under general anesthesia in thoracic surgery. Methods One hundred and twenty patients undergoing elective surgery under general anesthesia in the Department of Thoracic Surgery, the Sixth Medical Center of Chinese PLA General Hospital, from June 2021 to September 2021, were enrolled and randomly divided into control group (no dexmedetomidine perioperative), D1 group (dexmedetomidine 0.6 μg/kg intraoperatively), and D2 group (dexmedetomidine 0.6 μg/kg intraoperative, dexmedetomidine 2.4 μg/kg postoperative analgesia pump), 40 patients in each group. Perioperative anesthetic dosage, anesthetic time, operation time, time from operation completion to extubation, time from extubation to out-room and time from postoperative to discharge were compared among the three groups. The patients' average arterial pressure (MAP) and heart rate (HR) at entry (T₀), after intubation (T₁), immediately after dexmedetomidine pump injection (T₂), before catheterization (T₃), at exit (T₄), and 24, 48, 72 h after operation were recorded.Self-rating anxiety scale (SAS), visual analogue scale-anxiety (VAS-a), visual analogue scale (VAS), and sedation score (Ramsay)were measured before and 24, 48, 72 h postoperatively. Results No significant differences were observed in operation time,anesthesia time, time from operation completion to extubation, time from extubation to out-room and anesthesia dosage among the three groups (P>0.05), but the time from postoperative to discharge was significantly shorter in D2 group than in control group[(7.13±3.83) d vs. (8.93±3.67) d, P=0.027]. Compared with control group, the MAP of patients in D1 group and D2 group decreased at T₃ (P<0.05). No significant differences were observed in MAP, HR and Ramsay scores among the three groups at 24,48 and 72 h postoperatively (P>0.05). The SAS scores of patients in the three groups decreased significantly at 48 and 72 h after operation, and the decrease was most obvious in D2 group (P<0.05); The VAS-a score was significantly lower in D2 group than in control group and D1 group at 24, 48 and 72 h after surgery (P<0.05). The VAS scores of patients in the three groups decreased gradually at 48 and 72 h after surgery than that at 24 h after surgery (P<0.05). Multivariate linear regression analysis showed that age, sex and length of preoperative hospital stay were significantly correlated with preoperative anxiety in thoracic surgery patients(P<0.05). Conclusion Intra- and post-operative application of dexmedetomidine can significantly improve perioperative anxiety,synergistic analgesia and shorten postoperative hospital stay in patients of thoracic surgery.