Prunella vulgaris L. has been reported to exhibit certain remission potential for ulcerative colitis (UC). However, research that specifically focused on the P. vulgaris L. polysaccharides (PVP) is limited. The present study evaluated the anti-UC effects of PVP in mice with UC and investigated the underlying mechanism. The results indicated that PVP ameliorated the symptoms of UC by inhibiting colon shortening and weight loss, suppressing serum inflammatory cytokine (tumor necrosis factor (TNF)-α, interleukin (IL)-β, and IL-6) levels, preventing the activation of the colonic nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, and enhancing the expression of tight junction proteins to maintain gut barrier integrity. Additionally, PVP treatment significantly altered gut microbiota perturbation by decreasing the abundance of norank_f_norank_o_Clostridia_UCG-014, Rikenellaceae_RC9_gut_group, and unclassified_f_Prevotellaceae. In contrast, it increased the abundance of Lactobacillus, Desulfovibrio, Enterorhabdus, and norank_f_Oscillospiraceae. Metabolomic analysis revealed that 23 altered metabolites were selected as potential biomarkers of mice with UC following PVP treatment. These metabolites significantly enriched the pathways of glycerophospholipid metabolism and sphingolipid metabolism. Furthermore, there was a strong correlation between the alterations in gut microbiota at the genus level and the changes in metabolites. These results provide insights into the ameliorative effects of PVP on UC, suggesting its potential of PVP as a functional food or natural agent for UC management.