Inflammatory bowel disease (IBD) is an intestinal chronic inflammatory disease, and is related to imbalance of CD4 þ T subsets. However, the current treatments of chronic colitis are not ideal and have potential side effects. Therefore, more effective and safer biologically active substances which are extracted from natural plants have been widely concerned. In this study, it was found that Inonotus obliquus polysaccharides (IOP), the main bioactive constituent of Inonotus obliquus, can alleviate dextran sodium sulfate-induced chronic murine intestinal inflammation. Oral administration of IOP (100, 200, 300 mg/kg) can significantly reduce the disease active index and alleviate the pathological changes in colitis mice, where the tight junction proteins Occludin and ZO-1 losses in colon tissues were reduced. It can also regulate imbalanced Th1/Th2 and Th17/Treg in colon tissues, mesenteric lymph nodes and spleen using Reverse Transcription-Polymerase Chain Reaction detection and flow cytometry. Immunohistochemistry and western blot assays further revealed the modulatory effect of IOP on the p-STAT1, p-STAT6, p-STAT3 expression, which promoted the balance of Th1/Th2, Th17/Treg in the colon of chronic colitis mice. In short, these results indicated that IOP was potentially effective therapeutic agent for IBD.