Type 2 diabetes mellitus(T2DM) has developed into one of the three major diseases that threaten human health. Its pathogenesis is complex and regulated by multiple factors. The current research hotspots are closely related to the imbalance of intestinal microecology. Intestinal flora constitutes a complex ecosystem, and it plays a core regulatory role in maintaining the homeostasis of the host environment. Traditional Chinese medicine believes that stagnated heat is the key pathogenesis of incipient diabetes. As a famous classical formula for the treatment of T2DM, Dachaihu Decoction, which has the effect of Qingre Kaiyu, can regulate intestinal flora, repair damaged intestinal barrier, inhibit systemic inflammation, improve insulin sensitivity, regulate glycolipid metabolism, and achieve the purpose of preventing and treating T2DM. By exploring the mechanism of Dachaihu Decoction in improving intestinal flora and T2DM, it is expected to provide a theoretical support for clinical research and treatment.