Aberrant microbe-immune cell interaction is a predisposing factor in inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Cortex Periplocae is a famous traditional Chinese medicine with putative anti-rheumatoid arthritis and anti-dyspepsia effects. Here, we show that the Periploca sepium periplosides (PePs), a cardiac glycosides-free pregnane glycosides extract from root bark of Cortex Periplocae, alleviates colon inflammation, improves intestinal epithelial barrier function, and prevents colitis-associated tumorigenesis in mice with colitis and CAC. Mechanistically, PePs treatment modulates abnormal gut microbiota composition in model mice, especially enriches an anti-inflammatory commensal bacterium A. muciniphila BAA-835. We further demonstrate that the altered gut microbiota following PePs treatment plays an important role in modulation of intestinal Type 17 immunity in both colitis and CAC mouse model. Our results indicate that PePs may be used as a potential gut microbiota modulator to treat IBD and CAC. Keywords: Colitis; Colitis-associated cancer; Gut microbiota; Intestinal Type 17 immunity; Periploca sepium periplosides.