Objective To investigate the effects of dexmedetomidine(DEX)combined with sufentanil for patient-controlled intravenous analgesia(PCIA)on postoperative immune function and respiratory function recovery in patients undergoing thoracoscopic radical resection of lung cancer.Method From October 2020 to June 2022,92 ASA Ⅰ or Ⅱ patients scheduled for thoracoscopic radical resection of lung cancer were selected in our hospital,and they were randomly divided into sufentanil group(Group S)and DEX group(Group D)with 46 cases in each group.There was one case of postoperative bleeding in group S and one case of intraoperative bleeding in group D withdrew from the experiment.the group S postoperative PCIA with sufentanil injection 1.0 μg/kg pre day and tropisetron hydrochloride 20 mg/150 ml,Group D was treated with dexmedetomidine 1.0 μg/kg pre day and sufentanil injection 1.0 μg/kg pre day and tropisetron hydrochloride 20 mg/150 ml.At the four time points in preoperative day(T0),24 h(T1),48h(T2)and 72 h(T3)after operation.Rest and cough NRS scores and SAS scores were recorded and venous blood samples were taken to detected CD3+,CD4+,CD8+,CRP and PCT,Arterial blood gas analysis was detected to calculate OI;clinical pulmonary infection score(CPIS),the incidence of hypoxemia and pulmonary edema and adverse reactions including nausea and vomiting,drowsiness,bradycardia,respiratory depression and shivers were recorded at T2.Results Compared with S group,NRS score of resting or cough,SAS score,CRP and PCT of group D were significantly decreased at T,to T3(P＜0.05),while CD3+,CD4+,CD4+/CD8+and OI value was increased,CD8+was only lower in T1(P＜0.05).There were no significant differences in rest and cough NRS scores、SAS scores、CD3+、CD4+、CD8+、CD4+/CD8+、CRP,PCT and OI between the two groups at T0(P＞0.05).Compared with T0,Rest and cough NRS scores、CRP and PCT were significantly increased,CD3+、CD4+、CD4+/CD8+、OI and SAS scores were decreased in the two groups at T1-T3,CD8+increased only at T1 and T2(P＜0.05).Compared with group S[8(17.8％),(3.5±1.3)],the proportion of nausea and vomiting and CPIS score in group D[1(2.2％),(1.2±1.1)]was decreased(P＜0.05).There was no significant difference in the proportion of hypoxemia,pulmonary edema,drowsiness,bradycardia,respiratory depression and shivers(P＞0.05).Conclusion Dexmedetomidine combined with sufentanil patient-controlled analgesia has better analgesic and sedative effects,which can not only reduce the degree of immunosuppression caused by surgical trauma,but also reduce the adverse reactions of opioids,and is conducive to the recovery of postoperative respiratory function.It is a safer PCIA method after thoracoscopic radical resection of lung cancer.