Abstract: OBJECTIVE To investigate the protective effect and mechanism of Baicalin on rats with SAP complicated with peripancreatic infection. METHODS The rats model of SAP complicated with peripancreatic infection was established by injecting 5% sodium taurocholate and LPS into the pancreatic duct. The health status, pancreatic histological indicators, inflammatory cell number, and number of colonies in the peritoneal lavage fluid of the rats in each experimental group the control group（DZ）, the low dose group（L）, the medium dose group（M）, the high dose group（H）, the blank group（CK）were observed. The protein expression of IL-1β, IL-12, IL-17 A, and TGF-β1, the mRNA levels of IL-1β, IL-12, IL-17 A, and TGF-β1, and the levels of T lymphocyte subsets were determined. RESULTS The rats in the model group had fever, and there were significant differences in body temperature, body weight, and inflammatory cell counts in the peripheral blood among groups. The colony counts in the peritoneal lavage fluid of the control group were higher, and the baicalin treatment group had significantly lower counts（P＜0.05）; The expression levels of IL-1β, and TGF-β1 proteins in pancreas of SAP rats were significantly higher than those in the CK group, while the expression of IL-12 was significantly lower than those in the CK group（P＜0.05）. The differences in IL-17 A mRNA and TGF-β1 mRNA were significant（ P＜0.0,5）; The CD₃⁺, CD₄⁺, CD₄⁺/CD₈⁺ratio of rats in CK, DZ, L, M, and H groups increased, and the ratio of CD₈⁺ decreased, while the CD₃⁺, CD₄⁺, CD₄⁺/CD₈⁺ of rats in SAP group increased. CONCLUSION Baicalin mediated the transformation ratio of T lymphocyte subsets in rats with SAP complicated by peripancreatic infection, adjusted the levels of related cytokines, and played a positive immunomodulatory effect.