Purpose To evaluate the effect of dezocine on the postoperative ratio of Th1/Th2 cytokines in patients undergoing laparoscopic radical gastrectomy. Patients and Methods Sixty patients undergoing laparoscopic radical gastrectomy were randomly divided into two groups (n=30): dezocine group (Group D) and sufentanil group (Group S). They received patient-controlled intravenous analgesia (PCIA) after the operation with either dezocine 0.8 mg/kg (Group D) or sufentanil 2 µg/kg (Group S). Both groups also received ondansetron 8 mg diluted to 100 mL with saline. The primary outcome was the Th1/Th2 cytokines ratio at predetermined intervals, 30 min before the induction of general anaesthesia and 0, 12, 24 and 48 h after surgery. The secondary endpoints were patients’ pain scores, measured on a visual analogue scale (VAS) at predetermined intervals (0, 12, 24 and 48 h after surgery), and side effects at follow-up 48 h after surgery. Results The Th1/Th2 cytokines ratio in Group D was significantly higher than Group S ( P <0.05) 12, 24 and 48 h after the operation. There were no significant differences in VAS pain scores between groups at 0, 12, 24 and 48 h after surgery ( P >0.05). Compared to Group S, the incidence of postoperative nausea, vomiting and lethargy was significantly lower in Group D ( P <0.05). Conclusion Dezocine increases the ratio of Th1/Th2 cytokines, relieves postoperative pain and causes fewer side effects in patients undergoing laparoscopic radical gastrectomy.