This study explored the effects of L. plantarum BW2013 on mucosal integrity and gut microbiota of mice with dextran sulphate sodium (DSS) induced colitis. The results show that the clinical symptoms in DSS modelled ulcerative colitis (UC) were improved by L. plantarum BW2013 via decreasing disease activity index (DAI) scores and suppressing inflammatory cell infiltration. Furthermore, L. plantarum BW2013 decreased the levels of diamine oxidase (DAO) activity, myeloperoxidase (MPO) and D-lactic acid (DLA). The mRNA expression of ZO-1, occludin and claudin-1 was upregulated by L. plantarum BW2013, which also increased IL-10 and reduced TNF-α, IL-1β and IL-6 in the colon. 16S rDNA sequencing showed that L. plantarum BW2013 enhanced α-diversity. L.plantarum BW2013 upregulated significantly the abundance of unidentfied_Lachnospiraceae, Lactococcus, Rikenella, Lactobacillus and Odoribacter, which had an inhibitory effect on inflammation and a protective effect on the integrity of the mucosa. These results demonstrate that L. plantarum BW2013 alleviates DSS modelled UC by protecting mucosal integrity and ameliorating the composition of gut microbiota.