Abstract Diabetes is a worldwide metabolic diseases that requires adjustments in the blood glucose. Cornstarch is one kind of resistant starch, which helps to control postprandial glucose, and is a desired alternatives of carbohydrates for developing functional food. Herein, a cornstarch-based functional diet (CFD) was developed, and in this study we investigated the effects of CFD supplemented with tea polyphenols and EGCG on blood glucose and intestinal flora in diabetic mice. The results showed that diabetic mice had significant weight loss and serious hyperglycemia. The CFD or CFD supplemented with tea polyphenols and EGCG resulted in a trend toward reduced fasting blood glucose. Furthermore, diabetes had significant intestinal flora disturbance, with particularly increased levels of Bacteroidaceae, Helicobacteraceae, Ruminococcaceae, Enterobacteriaceae, Rikenellaceae and Saccharibacteria_genera_incertae_sedis, and decreased Prevotellaceae, Coriobacteriaceae, Bifidobacteriaceae and Verrucomicrobiaceae. Interesting, CFD supplemented with EGCG significantly increased levels of Prevotellaceae and Coriobacteriaceae, and decreased Lachnospiraceae, Helicobacteraceae, Ruminococcaceae and Saccharibacteria_genera_incertae_sedis compared to controls. CFD supplemented with tea polyphenols significantly increased the Coriobacteriaceae and Bifidobacteriaceae. The comprehensive analysis indicated that tea polyphenols and EGCG supplementation improved glucose metabolism, and reversed the sick changes of intestinal flora, suggesting they are two valuable additions to promote nutritional value of CFD.