BACKGROUND AND PURPOSE Diosmetin exhibits a series of therapeutic efficacy but little is known of its effects on colitis. EXPERIMENTAL APPROACH In this study, two mouse models of DSS (the concentration of 3% and 5%)-induced colitis and Caco2 and IEC-6 cells were employed. The 16S amplicon sequencing was used to assess Gut microbiota changes by diosmetin. Various physical signs of mice (body weight, colon length and DAI score), proinflammatory cytokines and antioxidant enzymes were tested. KEY RESULTS The results showed that diosmetin can markedly decrease the disease activity index and microscopic colon tissue damage, increase the expression of tight junction protein (Occludin, Claudin-1 and Zo-1) and reduce the secretion of proinflammatory cytokines. And diosmetin also significantly inhibited colon oxidative damage through adjusting the levels of intracellular ROS, mitochondrial ROS, GSH-Px, SOD, MDA and GSH in vitro and in vivo. Furthermore, it was found that diosmetin can modulate the abundance of Bacteroidetes, Actinobacteria, Cyanobacteria and Firmicutes, which were reported to be the crucial bacteria related to inflammatory bowel disease (IBD). CONCLUSIONS AND IMPLICATIONS Our data suggested that diosmetin ameliorated the colitis in mice induced by DSS in the potential mechanism that it alleviates intestinal epithelial barrier damage, inhibits the secretion of proinflammatory cytokines, decreases oxidative stress and modulates gut microbiota. It implies that diosmetin may be a novel candidate to alleviate DSS-induced colitis or a lead compound for future optimization and modification.