〔Abstract〕 Objective To investigate whether armillariella tabescens polysaccharides (ATPS) alleviates inflamma- tory responses and tissue damage in 5-fluorouracil ( 5-FU ) -induced chemotherapy-induced intestinal mucositis ( CIM) by inhibiting the TLR4 /MyD88 /NF-κB signaling pathway．Methods Thirty 8-weeks-old male C57BL/6J mice were randomly divided into five groups ( n = 6 per group) : control group，model group ，and ATPS-treated groups (low，medium，high dose : 100，200，400 mg / kg) ．Body weight changes were recorded ; Disease activity in- dex (DAI) scores were evaluated ; small intestinal length and histopathology were measured ; HE staining and his- topathological scoring were performed ; immunohistochemistry was used to detect the expression of tight junction pro- teins (ZO-1，Occludin) in the small intestine ; serum levels of inflammatory cytokines interleukin-6 ( IL-6 ) and tumor necrosis factor-alpha (TNF-α) were analyzed by enzyme-linked immunosorbent assay (ELISA) kit ; Western blot was employed to quantify ZO-1，Occludin，and TLR4 /MyD88 /NF-κB pathway-related protein TLR4，MyD88，NF-κB p65，IκBα , p-NF-κB p65，p-IκBα protein expression．Results Compared with the control group，mice in the model group exhibited significant reductions in body weight ，elevated DAI scores ，shortened small intestinal length，increased histopathological scores，marked downregulation of ZO-1 and Occludin expression，and elevated levels of inflammatory cytokines TNF-α and IL-6．Additionally，protein expression levels of TLR4，MyD88，p-NF- κB p65，and p-IκBα were significantly upregulated ( all P ＜0. 01 ) ． In contrast ，mice in ATPS-treated groups showed dose-dependent improvements，attenuated weight loss，reduced DAI scores，restored intestinal length，de- creased histopathological scores，upregulated ZO-1 and Occludin expression，reduced TNF-α and IL-6 levels，and downregulated TLR4，MyD88，p-NF-κB p65，and p-IκBα protein expression (all P＜0. 01) ．Conclusion ATPS alleviates 5-FU-induced CIM by inhibiting the TLR4 /MyD88 /NF-κB signaling pathway．