Objective To systematically evaluate the efficacy and safety of injected cyclooxygenase-2 inhibitor for acute postoperative pain. Methods We electronically searched PubMed, EBSCO, Springer, Ovid and CNKI databases from 1999 through Jan. 2009 to identify randomized controlled trials (RCTs) about cyclooxygenase-2 inhibitor or parecoxib sodium for acute postoperative pain. The methodological quality of included RCTs were assessed, and the data was extracted by two reviewers independently according to the Cochrane Handbook. The homogeneous RCTs were pooled using RevMan software, and the non-homogeneous studies evaluted using descriptive qualitative analysis. Results Seven RCTs involving 1939 patients met the inclusion criteria. The results of meta-analyses showed that: ① Efficacy: The comparison of PCA combined parecoxib sodium (successively injected less than 3 days) i.v. with PCA alone: after 24, 48, and 72 hours of the initial dose of parecoxib 40 mg i.v., the percentage of the patients’ global evaluation of study medication (PGESM) described effective (excellent and good) was higher than that of the control group [RR (95%CI) were 1.41 (1.13, 1.75), 1.25 (1.15, 1.35), and 1.30 (1.21, 1.40) respectively]; the percentage of the PGESM described ineffective (fair and poor) was lower than that of the control group [RR (95%CI) were 0.43 (0.26, 0.72), 0.44 (0.34, 0.57), and 0.33 (0.23, 0.48) respectively]. ② Safety: Combination of PCA with parecoxib sodium could lessen the incidence of postoperative fever (RR=0.34, 95%CI 0.22 to 0.53) and nausea and vomiting (RR=0.69, 95%CI 0.57 to 0.83), but not statistically decrease of respiratory depression (RR=0.84, 95%CI 0.38 to 1.83), pruritus (RR=0.91, 95%CI 0.54 to 1.52), and headache (RR=0.77, 95%CI 0.47 to 1.28). Conclusion The combination of PCA with parecoxib sodium successively injected less than 3 days can significantly increase the scores of PGESM, and does not increase the incidence of adverse effects or postoperative complications, and also has the advantage of decreasing postoperative fever, nausea and vomiting.