Inflammatory bowel disease (IBD) is a disease caused by a dysregulated immune with unknown etiology. Hericium erinaceus (H. erinaceus) is a Chinese medicinal fungus, with the effect of prevention and treatment of gastrointestinal disorders. In this study, we have tested the anti-inflammatory effect of polysaccharide of H. erinaceus (HECP, Mw: 86.67 kDa) in the model of dextran sulfate sodium (DSS)-induced colitis in C57BL/6 mice. Our data indicated that HECP could improve clinical symptoms and down-regulate key markers of oxidative stresses, including nitric oxide (NO), malondialdehyde (MDA), total superoxide dismutase (T-SOD), and myeloperoxidase (MPO). HECP also suppressed the secretion of interleukin (IL)-6, interleukin (IL)-1β, tumor necrosis factor (TNF)-α and the expression of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and decreased the expression of related mRNA. Meanwhile, HECP blocked phosphorylation of nuclear factor-κB (NF-κB) p65, NF-κB inhibitor alpha (IκB-α), mitogen-activated protein kinases (MAPK) and Protein kinase B (Akt) in DSS-treated mice. Moreover, HECP reversed DSS-induced gut dysbiosis and maintained intestinal barrier integrity. In conclusion, HECP ameliorates DSS-induced intestinal injury in mice, which suggests that HECP can serve as a protective dietary nutrient against IBD.