Background: Multimodal postoperative analgesia with intravenous ibuprofen can reduce the consumption of opioids and reduce the postoperative pain intensity. Recommended dose in the USA and Europe is 800 mg every 6 hours for the management of moderate to severe postoperative pain. The purpose of this study was to investigate whether 800 mg is needed in the Chinese population.Methods: This is a multicenter, randomized, controlled multi-center trial. Adult patients (18-65 years of age) scheduled for abdominal or orthopedic surgery under general anesthesia with endotracheal intubation were eligible. Subjects were randomized at a ratio of 1:1:1 to receive ibuprofen at 400 or 800 mg or saline every 6 hours for 48 hours after the operation. All subjects received morphine access through patient-controlled intravenous analgesia (PCIA) device, which was set as background infusion rate 0.5 mg/h, bolus 1 mg, 5-minute lock interval and 20-mg 4-hour limit. The primary endpoint was morphine consumption within the first 24 hours after surgery. Results: A total of 396 patients were enrolled (180 men, 216 women; 46±12.4 years of age; 106 patients receiving abdominal surgery, and 290 patients receiving orthopedic surgery). The number of patients was 131 in the placebo group, 132 in the 400-mg group, and 133 in the 800-mg group. The 3 groups did not differ in age, sex, BMI and the type of surgery. Median 24-hour morphine consumption was 39.1 mg (IQR: 29.7, 61.7) mg in the placebo control, 29.8 mg (IQR: 24.3, 43.7) mg in the 400-mg group, and 28.0 mg (IQR: 24.1, 35.9) in the 800-mg group (P<0.001 for comparisons between placebo versus 400 and 800 mg ibuprofen). There was no significant difference between the two ibuprofen groups (P=0.125). Analgesia-related adverse events did not differ among the 3 groups.Conclusions: Intravenous ibuprofen at either 400 or 800 mg every 6 hours could reduce postoperative morphine consumption, with apparently equal efficacy in Chinese population.