OBJECTIVE： To compare the effects of dezocine and nalbuphine on patient-controlled intravenous analgesia （PCIA） in patients undergoing cesarean section. METHODS： A total of 97 patients undergoing selective cesarean section were selected from our hospital during Jun. 2015 to Mar. 2017. They were divided into dezocine group （52 cases） and nalbuphine group （45 cases） according to lottery. Both groups received cesarean section under combined spinal-epidural anesthesia， and then given PCIA pump immediately after surgery. The pump of dezocine group was Dezocine injection 0.5 mg/kg+Tropisetron hydrochloride injection 10 mg； that of nalbuphine group was Nalbuphine hydrochloride injection 2 mg/kg+Tropisetron hydrochloride injection 10 mg. Both groups of analgesic drugs were diluted 100 mL with 0.9％ sodium chloride injection， constant infusion of liquid medicine at rate of 2 mL/h， adding 0.5 mL additionally each time， for consecutive 48 h. VAS score and Ramsay sedation score of resting pain， dynamic pain and uterine contraction pain were performed in 2 groups 4， 8， 12， 24，48 h after surgery. The serum levels of PRL were determined 30 min before surgery and 24， 48 h after surgery. The initial time of lactation and ADR were recorded in 2 groups. RESULTS： VAS score of resting pain and uterine contraction pain at 4， 8， 12 h after operation and that of dynamic pain at 4，8，12，24 h after operation were significantly lower in dezocine group than nalbuphine group， with statistical significance （P＜0.05）. There was no statistical significance in VAS score between 2 groups at other time points （P＞0.05）. As time went on， the VAS scores of the two groups decreased significantly at each time point， and the difference was statistically significant （P＜0.05）. The serum levels of PRL in 2 groups 24 and 48 h after operation were significantly higher than 30 min before operation， with statistical significance （P＜0.05）. There was no statistical significance in serum level of PRL between 2 groups at same time point（P＞0.05）. There was no statistical significance in Ramsay score， initial time of lactation or the incidence of ADR between dezocine group and nalbuphine group （P＞0.05）. CONCLUSIONS： Both dezocine and nalbuphine are effective analgesia drugs of PCIA in patients undergoing cesarean section. Early postoperative analgesic effect of dezocine is superior to nalbuphine. They have similar effects on long-term analgesia and postoperative sedative， serum level of PRL， initial time of lactation， as well as safety.