Intact epithelial barrier and mucosal immune system are crucial for maintaining intestinal homeostasis. Previous study indicated that Dendrobium officinale polysaccharides (DOPS) can regulate immune responses and inflammation to alleviate experimental colitis. However, it remains largely unknown whether DOPS can suppress AOM/DSS-induced colorectal cancer (CRC) model through its direct impact on intestinal barrier function and intestinal mucosal immunity. Here, we demonstrated the therapeutic action of DOPS for CRC model and further illustrated its underlying mechanisms. Treatment with 5-aminosalicylic acid (5-ASA) and DOPS significantly improved the clinical signs and symptoms of chronic colitis, relieve colon damage, suppress the formation and growth of colon tumor in CRC mice. Moreover, administration of DOPS effectively preserved the intestinal barrier function via reducing the loss of zonula occludens-1 (ZO-1) and occludin in adjacent tissues and carcinomatous tissues. Further studies demonstrated that DOPS improved the metabolic ability of tumor infiltrated CD8+ cytotoxic T lymphocytes (CTLs) and reduced the expression of PD-1 on CTLs to enhance the anti-tumor immune response in the tumor microenvironments (TME). Together, the conclusions indicated that DOPS restore intestinal barrier function and enhance intestinal anti-tumor immune response to suppress CRC, which may be a novel strategy for the prevention and treatment of CRC. Copyright © 2019 Elsevier Ltd. All rights reserved.