Purpose To investigate the effectiveness of sufentanil patient-controlled intravenous analgesia pump (PCIA) and background infusion in patients of post-cesarean analgesia. Patients and Methods This trial compared two groups of women undergoing cesarean section and receiving PCIA: no background infusion group (n=30), 6-min lockout time, and background infusion group (n=30), 2 mL/h infusion, 10-min lockout time. Both groups with 2 μg/kg sufentanil was diluted to 100 mL with normal saline. VAS scores at rest at 36 h was the primary endpoint. The secondary endpoints were the VAS scores at rest at 6, 12, and 24 h, the total amount of sufentanil consumed, the Ramsay sedation score (RSS) assessed at the same time points, postpartum bleeding within 24 h, the injection/attempt (I/A) ratio, BP and HR, PONV, side effects of sufentanil. Results Compared with the no background infusion group, the background infusion group showed lower VAS pain scores at 6, 12, and 24 h (P<0.01), but no differences at 36 h (95% CI = −0.5–0.8. P>0.05). Attempts, injections, and total sufentanil consumption were significantly different between the two groups (P<0.001), but without difference in I/A. Bleeding was less in the background infusion group at 1 h (P=0.03). The minimal respiration rates were not significantly different between groups. Conclusion Background infusion increased the total consumption of sufentanil within 36 h after cesarean section. Although it did not reduce uterine contraction pain and wound pain at 36 h, it significantly reduced the pain at 6, 12, and 24 h after cesarean section. It improved patient satisfaction and reduced the amount of bleeding after 1 h. Importantly, it did not increase the incidence of hypertension, PONV and respiratory depression.