Black wolfberry (Lycium ruthenicum) is a widely consumed food known for its pharmacological properties, particularly its anti-inflammatory and antioxidant effects. This study investigates the therapeutic potential of black wolfberry polysaccharides (LRP) and anthocyanins (LRA) in treating ulcerative colitis, a chronic inflammatory bowel disease. Using a DSS-induced mouse model of colitis, we administered varying doses of LRP and LRA and evaluated their effects on disease activity, inflammation, gut barrier function, and microbiota composition. LRP demonstrated dose-dependent efficacy, with the 200 mg/kg dose showing the most significant reduction in the disease activity index (DAI), improvement in histopathology, and restoration of tight junction protein expression. In contrast, LRA exhibited an inverted U-shaped response, with the 100 mg/kg dose being the most effective. Additionally, LRP treatment modulated cytokine levels, promoting an anti-inflammatory response, and significantly restored gut microbiota balance by increasing Muribaculaceae and Limosilactobacillus while reducing Bacteroides and Helicobacter. Fecal microbiota transplantation (FMT) experiments further confirmed that the therapeutic effects of LRP are microbiota-dependent. These findings suggest that LRP, a polysaccharide derived from black wolfberry, offers a dietary intervention for colitis through immune modulation and gut microbiota restoration.