Objective The matrix metalloproteinase 9 (MMP-9) plays an important role in the systemic inflammatory response syndrome and organ damages in severe acute pancreatitis (SAP).The aim of the present study was to investigate the impact of Chaiqinchengqi decoction (CQCQD) on serum MMP-9 in SAP patients,Methods Thirty-five SAP patients hospitalized in West China Hospital from September 1,2008 to February 28,2009,were randomized into the treatment group (n=18) and the placebo control group (n=17).The patients in the treatment group) were administered with CQCQD by gastric perfusion (50 mL/2h×7) and retention enema (200mL/6h×7).The two groups had similar baseline information.The clinical data and the serum C-reactive protein (CRP),MMP-9 and interleukin (IL-6) on the first,3rd,5th and 7th day after admission were compared.