Abstract: Pai-Nong-San (PNS), a prescription of traditional Chinese medicine, has been used for years to treat abscessation-induced diseases including colitis and colorectal cancer. This study was aimed to investigate the preventive effects and possible protective mechanism of PNS on a colitis-associated colorectal cancer (CAC) mouse model induced by azoxymethane (AOM)/dextran sodium sulfate (DSS). The macroscopic and histopathologic examinations of colon injury and DAI score were observed. The inflammatory indicators of intestinal immunity were determined by immunohistochemistry and immunofluorescence. The high throughput 16S rRNA sequence of gut microbiota in the feces of mice was performed. Western blot was used to investigate the protein expression of the Wnt signaling pathway in colon tissues. PNS improved colon injury, as manifested by the alleviation of hematochezia, decreased DAI score, increased colon length, and reversal of pathological changes. PNS treatment protected against AOM/DSS-induced colon inflammation by regulating the expression of CD4⁺ and CD8⁺ T cells, inhibiting the production of HIF-α, IL-6, and TNF-α, and promoting the expression of IL-4 and IFN-γ in colon tissues. Meanwhile, PNS improved the components of gut microbiota, as measured by the adjusted levels of Firmicutes, Bacteroidetes, Proteobacteria, and Lactobacillus. PNS down-regulated the protein expression of p-GSK-3β, β-catenin, and c-Myc, while up-regulating the GSK-3β and p-β-catenin in colon tissues of CAC mice. In conclusion, our results suggested that PNS exhibits protective effect on AOM/DSS-induced colon injury and alleviates the development of CAC through suppressing inflammation, improving gut microbiota, and inhibiting the Wnt signaling pathway.