To observe the effects of Kuijie Formula on the expression of inflammatory factors and JAK2，STAT3 in ulcerative colitis rats and to explore its mechanism.Methods:TNBS solution was used to build the ulcerative colitis rats models and Kuijie Formula was administrated by gavage everyday.Enzyme-Linked Immuno Sorbent Assay(ELISA)method was used to test UC rat’s TNF-α，IL-6，IL-10，IL-4； the pathological changes of the colon in rats was observed by naked eyes.JAK2 and STAT3 were determined by immunohistochemical staining(SP method).Results:Kuijie Formula can reduce the TNF-α，IL-6 levels and level up the IL-10，IL-4 in serum significantly(P<005).It can also reduce the DAI and CMDI sores of the rats’ colon as well as the expression of JAK2 and STAT3 in colon tissues.Conclusion:Kuijie Formula can regulate the balance of pro-inflammatory and anti-inflammatory cytokines in UC rats，slow down the inflammatory response and improve the colonic ulcer damage in UC rats.Its mechanism may be related to reducing the inflammatory response and the expression of JAK2 and STAT3