Objective: To investigate the effect of Modified Xiaochaihu Decoction (MXD,加味小柴胡汤)on collagen degradation in rats with chronic pancreatitis (CP).Methods: Rats were injected dibutyltin dichloride (DBTC,7 mg/kg of body weight) into the right caudal vein to induce CP model.Thirty heallhy male Wistar rats were randomly divided into three groups by a random number table: the control,the model and the treatment groups.Rats of treatment group were administered MXD (10 g/kg of body weight) orally once daily starting from the day post-model establishment.Pancreatic tissues were harvested after 28-day feeding and fibrosis was evaluated by picro-sirius red staining.The contents of collagen type Ⅰ and Ⅲ were detected using enzyme-linked immunosorbent assay (ELISA),the expression of matrix metalloproteinase 13 (MMP13) and tissue inhibitor of metalloproteinase 1 (TIMP1) was analyzed by Western blot and real-time polymerase chain reaction (PCR).Results: The fibrosis scoring of pancreatic tissues,the concentrations of collagen type Ⅰ and Ⅲ,the expression levels of MMP13 and TIMP1 proteins and mRNA in the model group were all increased compared with the control group (P＜0.05).After treatment with MXD,the fibrosis scoring of pancreatic tissues,the concentrations of collagen type Ⅰ and Ⅲ,the expression levels of MMP13 proteins and mRNA in the teatment group were all decreased compared with the model group (P＜0.05),but there were no significant differences in the expression levels of TIMP1 proteins and mRNA (P＞0.05).Conclusion: MXD could promote collagen degradation and reverse pancreatic fibrosis in CP rats via a mechanism involve up-regulation of MMP13 expression.