Abstract: This study aimed to investigate the effect of epigallocatechin-3-gallate (EGCG) on dextran sulfate sodium (DSS)-induced colitis and gut microbiota in mice. The C57BL/6 male mice were divided into normal control group, enteritis model group and EGCG treatment group (50 mg/kg), 10 mice in each group, and were administered orally for 9 consecutive days. The improvement effect of EGCG on DSS-induced colitis in mice was evaluated by weighing the weight of the mice, observing and recording the fecal viscosity and fecal bleeding of the mice, measuring the length of the colon in the mice and detecting inflammatory factors in the serum. The effect of EGCG on the gut microbiota of DSS-induced colitis mice was evaluated by analyzing colon pathological morphology, expression of tight junction proteins, the diversity and structure of gut microbiota. The results showed that EGCG effectively improved the adverse reactions in DSS-induced colitis mice such as weight loss, diarrhea, blood in the stool, and colon, and alleviated systemic chronic inflammation and intestinal barrier damage in DSS-induced colitis mice. Furthermore, EGCG also ameliorated the gut microbiota disturbance, restored gut microbiota diversity, decreased the relative abundance of Firmicutes, increased the relative abundance of Bacteroidetes, promoted the proliferation of beneficial bacteria such as Akkermansia, Alistipes and Bacteroides, and inhibited the growth of harmful bacteria including Desulfovibrio, Escherichia-Shigella and Helicobacter. Therefore, EGCG effectively ameliorated DSS-induced colitis in mice by protecting the intestinal barrier and regulating gut microbiota disturbance.