Inflammatory bowel disease (IBD) relates to gut microbiota dysbiosis, bile acid (BA) disturbance and intestinal barrier impairment. We purified a fructose-dominant (Fru 93.63%) low-molecular-weight Polygonatum sibiricum polysaccharide (PSP). In 3% DSS-induced colitis in C57BL/6 mice, PSP (400 mg/kg/day) alleviated symptoms. Multi-omics showed PSP reversed DSS-induced disorders, regulated BA biosynthesis, restored barrier function and mitigated colitis, supporting its IBD intervention potential.