Inflammatory bowel disease(IBD)is an autoimmune disease and its etiology has not yet been clarified. Dysregulated immune responses resulted from complex interactions among genetic factors,intestinal flora and environmental cues have been considered as the etiology of IBD. Recently,the relationship between Th17 cells and IBD has become a hotspot of study,and more and more studies showed that Th17 cells and their related cytokines regulated by intestinal flora contributed to the pathogenesis of IBD. This article reviewed the role of Th17 cells and intestinal flora in the pathogenesis of IBD.