Arsenic, a known environmental carcinogen, disrupts intestinal homeostasis, posing a significant threat to human health. Mitigating its toxic effects is crucial, and this study explores the potential of swim bladder sulfated glycosaminoglycan (SBSG) in achieving this. Our previous in vitro studies have shown SBSG to ameliorate arsenic-induced damage in intestinal epithelial cells, but its in vivo effects remain elusive. The current investigation demonstrates that SBSG exhibits a beneficial prebiotic action in vivo, regulating gut microbiota, metabolites, and intestinal barrier function to counter arsenic's adverse effects. Specifically, SBSG regulates microbiota composition, suppressing pathogenic species like Alistipes and Candidatus_Saccharimonas while promoting beneficial ones such as Ruminococcus and Akkermansia. In the colon, SBSG fermentation enhances the production of short-chain fatty acids (SCFAs), leading to upregulation of GPR43, GPR109A, and Olfr78 receptors. Additionally, SBSG strengthens the intestinal barrier by increasing the expression of Claudin-1, Occludin, and ZO-1, and enhances mucin gene expression (MUC-1 and MUC-2) to address chemical barrier disruptions. Immunologically, SBSG modulates the RORγt/Foxp-3 pathway and the TLR4/MyD88/NF-κB signaling cascade, regulating the immune barrier. These findings suggest that SBSG could be a promising prebiotic candidate for maintaining intestinal health and may serve as a dietary supplement or adjunct in heavy metal detoxification therapies.