Colitis is a multifactorial inflammatory bowel disease (IBD) involving intestinal barrier dysfunction, immune dysregulation, oxidative stress, and microbiota imbalance. Lactobacillus salivarius (L. salivarius), a probiotic with antioxidative and anti-inflammatory properties, was evaluated in a mouse model of DSS-induced colitis. Treatment with L. salivarius significantly reduced weight loss, colon shortening, and disease activity index, while improving histopathological damage. DSS-induced colitis exhibited significant oxidative stress, evidenced by decreased total antioxidant capacity, increased malondialdehyde (MDA), and reduced activity of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). After the intervention of L. salivarius, MDA levels in colon tissues decreased significantly, while SOD and GSH-Px activities increased significantly. In DSS-induced colitis models, the expression of pro-inflammatory cytokines (such as TNF-α, IL-6, IL-1β) was significantly increased, while the expression of anti-inflammatory cytokine IL-10 was decreased. After the intervention of L. salivarius, the level of proinflammatory factors was significantly down-regulated, while the level of IL-10 was up-regulated. DSS treatment leads to a significant imbalance in the intestinal microbiota, characterized by an increase in the ratio of Firmicutes to Bacteroidetes (F/B ratio). The abundance of pathogenic bacteria (Alistipes, Candidatus_Soleaferrea, Frisingicoccus, Romboutsia, Streptococcus) increased, while beneficial bacteria (Anaerotruncus, Rikenella) decreased. After probiotic administration, the F/B ratio was restored significantly, and the abundance of important beneficial bacteria increased while the abundance of pathogenic bacteria decreased. These results suggest that L. salivarius alleviates DSS-induced colitis by enhancing antioxidant defense, regulating inflammatory responses, and restoring gut microbiota balance. This probiotic may offer a promising therapeutic strategy for managing ulcerative colitis (UC).