OBJECTIVE： To observe the efficacy of patient controlled intravenous analgesia （PCIA） of dexmedetomidine combined with sufentanil for postoperative analgesia of patients with esophageal cancer， and its effects on immune function of the body. METHODS： Totally 120 cases of esophageal cancer patients who received surgical treatment in our hospital were collected from Jan. 2015 to Jan. 2107， and then divided into control group and observation group according to random number table， with 60 cases in each group. After surgery， all patients received PCIA. Control group was given Sufentanil citrate injection 2 μg/（kg·d）+Tropisetron hydrochloride injection 15 mg+0.9％ Sodium chloride injection as PCIA solution 100 mL. Observation group was given Dexmedetomidine hydrochloride injection 0.75 μg/（kg·d）+Sufentanil citrate injection 2 μg/（kg·d）+Tropisetron hydrochloride injection 15 mg+0.9％ Sodium chloride injection as PCIA solution 100 mL. The background dose， single dose and locking time PCIA of 2 groups were 2 mL/h， 0.5 mL and 15 min. VAS score of 2 groups were observed after surgery. The plasma levels of IFN-γ and IL-10， CD3+T cell， CD4+T cell， CD8+T cell， CD4+/CD8+， the occurrence of ADR were observed before and after surgery. RESULTS： VAS score of observation group was significantly lower than control group 6， 12， 24， 48 h after surgery （P＜0.05）， and decreased gradually as time. The plasma level of IFN-γ in 2 groups 6 h after surgery， that of control group 12， 24， 48 h after surgery were significantly higher than before surgery， but the observation group 6， 12， 24， 48 h after surgery was significantly lower than control group. The plasma level of IL-10 in 2 groups 12， 24， 48 h after surgery were significantly higher than before surgery， and the observation group 6， 12， 24， 48 h after surgery was significantly higher than control group （P＜0.05）. Plasma level of CD3+T cell of control group 12， 24， 48 h after surgery were lower than before surgery， but the observation group was significantly higher than control group 6， 12， 24 h after surgery. Plasma level of CD4+T cell of 2 groups 12， 24 h after surgery were significantly lower than before surgery， but the observation group was significantly higher than control group 6， 12， 24 h after surgery. Plasma level of CD8+T cell of control group 24 h after surgery， those of observation group 12， 24 h after surgery were significantly lower than before surgery； the observation group was significantly lower than control group 12， 24 h after surgery. Plasma level of CD4+/CD8+ of control group 12， 24 h after surgery were significantly lower than before surgery； those of observation group 12， 24 h after surgery were significantly higher than before surgery， and CD4+/CD8+ level 6， 12， 24 h after surgery were also higher than control group （P＜0.05）. There was no statistical significance in the incidence of ADR between 2 groups （P＞0.05）. No respiratory depression occurred in neither groups after surgery. CONCLUSIONS： PCIA of dexmedetomidin combined with sufentanil is significantly effective for postoperative analgesia of patients with esophageal cancer， it can improve the immune function of patients without enhancing the occurrence of ADR.