Intestinal flora is a complex micro-ecosystem in human body, which is called the second genome of human body. Intestinal flora imbalance plays an important role in the occurrence and development of gastric cancer through circulation, metabolism and immunity. Gastric cancer is associated with dysbacteriosis. Traditional Chinese medicine (TCM) compounds in Buyang Yiwei Decoction can reduce the clinical signs and symptoms of gastric cancer by regulating intestinal microbiota, alleviate the adverse reactions of gastric cancer after radiotherapy and chemotherapy, and improve the quality of life of patients. This article reviews whether Buyang Yiwei Decoction can reduce the risk of gastric cancer or play a therapeutic role in gastric cancer by improving the intestinal microbiota.