Ｏｂｊｅｃｔｉｖｅ　To evaluate the efficacy of patient-controlled intravenous analgesia(PCIA) using dexmedetomidine (Dex) combined with sufentanil and the effect on postoperative immune function and pulmonary complications in patients undergoing operation of lung cancer.　Methods　One hundred and twenty patients with lung cancer were recruited in this study, and randomly divided into two groups for PCIA after thoracoscopic lobectomy, group A(Dex and sufentanil group, n=60) and group B (sufentanil group, n=60). VAS scores, observer's assessment of alertness/sedation(OAA/S) scores, and pulmonary complications were recorded after operation. And the number of natural killer (NK) cells, the level of interferon-γ (IFN-γ) or IL-4, and the ratio of T helper cells 1/T helper cells 2(Th1/Th2) were measured perioperation.　Results　There was no significant difference between the two groups in VAS, OAA/S scores and additional analgesics(P>0.05). The cases of pruritus, postoperative nausea and vomiting(PONV), and pulmonary complications in group B were 8, 16, 8 and 11, while they were 0, 2, 2 and 3 in group A, respectively(P<0.05), and there were significantly difference between the two groups. The number of NK cells, IFN-γ level and radio of Th1/Th2 were significantly decreased, and IL-4 level was significantly increased in both groups as early as the end of surgery (P<0.05), and they all restored in 1 week after surgery in group A(P>0.05), however, in group B, they all restored in 2 weeks after surgery(P>0.05).　Conclusions　Dex combined with sufentanil is efficient for PCIA in patients undergoing thoracoscopic lobectomy, it could decrease the incidence of pruritus, PONV and pulmonary complications, and promote the recovery of immune function.