Abstract: Objective To assess the effect of ulinastatin on acute respiratory distress syndrome (ARDS). Methods A meta-analysis was performed for the clinical trials on ulinastatin in treatment of ARDS covered in PubMed, Embase, CBMdisk, CNKI and Wanfang Database before May 2012 with the software of ReviewManager4.2 on Cochrane Cooperation Network. The curative effect indexes of ulinastatin included respiratory frequency, PaO₂/FiO₂, PaCO₂ and mortality. Results Meta analysis showed that the mean respiratory frequency and mortality were lower whereas the mean PaCO₂ and PaO₂/FiO₂ were higher in ulinastatin treatment group than in control group 7 days after ulinastatin treatment (WMD=-5.74, P=0.003; RR=0.62, P=0.04; WMD=4.78, P＜ 0.000 01; WMD=59.94, P＜ 0.000 01). Conclusion Ulinastatin can significantly improve the pulmonary ventilation and reduce the mortality of ARDS patients.