Phellinus linteus (Agaricomycetes) is a valuable medicinal mushroom traditionally used as a food supplement and medicinal ingredient. Polysaccharides of Ph. linteus (PLP) possess strong anti-inflammatory effects and gut microbiota modulating properties. However, the mechanism of its efficacy in ulcerative colitis (UC) remains unclear. This study utilized 1mM H2O2 to induce an in vitro model of UC in Caco-2 cells. Additionally, a 3% solution of dextran sulfate sodium salt (DSS) was employed to establish an in vivo UC model in mice. After treating the cells with PLP at various concentrations, there was a significant reduction in the mRNA expression of TNF-alpha and IL-6, and the nuclear factor-kappaB (NF-kappaB) signaling pathway was also inhibited. Concurrently, symptoms such as colon shortening, weight loss, and a decrease in disease activity index (DAI) scores were significantly improved in UC mice. Additionally, the treatment led to downregulated expression of TNF-alpha and IFN-gamma mRNA in colon tissues. PLP had shown potential in reducing inflammation and oxidative stress in Caco-2 cells, demonstrating therapeutic effects in treating UC-like inflammation by inhibiting the NF-kappa signaling pathway and activating the nuclear factor erythroid derived 2-like 2(Nrf2)/heme oxygenase-1(HO-1) signaling pathway. These findings suggest that PLP has great potential for further investigation and development in UC treatment.