Ｏｂｊｅｃｔｉｖｅ　Postoperative analgesia is one of the concerns of anesthesiologists and patients. The aim of this study is to investigate the effect and safety of different concentration of sufentanil for postoperative patient-controlled intravenous analgesia （PCIA） after gynecologic surgery， providing the basis of individualized dosage for future clinical applications.　Methods　Forty-eight ASA Ⅰ-Ⅱ patients （18 y-65 y of age） scheduled for elective gynecological surgery were recruited and randomly assigned to three groups receiving patient-controlled analgesia（n=16）， the Suf1 group （loading dose of sufentanil 0.25 μg/kg， the concentration of sufentanil is 0.02 μg·kg-1·ml-1）， the Suf2 group（loading dose of sufentanil 0.25 μg/kg, with sufentanil's concentration 0.022 5 μg·kg?蛳1·ml?蛳1), and the control group（the first dose of fentanyl 2.5 μg/kg, fentanyl 0.2 μg·kg?蛳1·ml?蛳1）. PCIA was administrated with continual infusion rate of 2 ml/h, bolus injection of 0.5 ml and lockout time of 15 min. Visual analogue scale（VAS） at rest and on movement and sedation scores were assessed at 1, 2, 4, 8, 12, 24 h and 48 h postoperatively. For each pain assessment, the patient's vital signs and the side-effects from sufentanil（including nausea, emesis, pruritus, and respiratory depression） were recorded.　Results　Compared to the control group, the Suf2 group showed significant lower VAS scores at rest 12 h postoperatively［VAS in Control group： （2.0±0.6）, VAS in Suf2 group： （0.9±0.6）, P<0.05］ and VAS scores on movement 24 h postoperatively［such as 24 h after the postoperative analgesia, control group： （2.6±0.7）， Suf2 group： （2.0±1.0）， P<0.05］. Compared to the Suf1 group, both the VAS scores at rest［such as 48 h after the postoperative analgesia, Suf1 group： （1.2±0.5）, Suf2 group： （0.5±0.7）, P<0.05］ and on movement ［such as 48 h after the postoperative analgesia, Suf1 group： （2.1±0.6）, Suf2 group：（1.8±0.8）, P<0.05］ decreased significantly in the Suf2 group （P<0.05）. All these data indicated that the concentration of sufentanil used in the Suf2 group could provide adequate pain control during 12 h after postoperative analgesia compaed to the other two groups.　Conclusions　The dosage of sufentanil of 0.022 5 μg·kg-1·ml-1 could provide better analgesia, sedation， with lower incidence of side-effects in postoperative pain relief after gynecologic surgery.