[Objective] This study aimed to investigate the effects of Yam Polysaccharide (YP) on ulcerative colitis (UC) mice. [Methods] The study included a blank group, YP group, DSS group, and DSS+YP group. The UC model was established by administering DSS water solution, and the treatment group received oral administration of YP for 7 days. Measurement of body weight, DAI score, inflammatory factors in the colon, NLRP3 inflammasome, and HE staining were conducted to evaluate the effects. RAW 264.7 macrophages were treated with 1 μg/mL lipopolysaccharide (LPS) for 24 h to establish the cell inflammation model in vitro. A certain concentration of YP solution was added to the culture medium and incubated with LPS for 24 h. The contents of IL-1β, IL-6 and TNF-α in the cell culture supernatance were detected by enzyme-linked immunosorbent assay. The expression level of NLRP3 inflammator-related protein was analyzed by Western blotting. [Results] Compared to the blank group, the DSS group showed weight loss, extensive ulceration in staining, increased DAI score, and elevated levels of inflammatory factors. Compared to the DSS group, the DSS+YP group showed significant improvement in intestinal damage, and the expression of IL-1β, IL-6, TNF-α, and activation of NLRP3 inflammasome signaling were significantly inhibited in intestinal tissues. In the cell inflammation model, YP pretreatment significantly suppressed the secretion of IL-1β, IL-6, TNF-α induced by LPS, as well as the expression of NLRP3 protein. [Conclusion] YP can improve DSS-induced UC in mice by inhibiting the activation of NLRP3 inflammasome.