Abstract: Irritable bowel syndrome is a kind of human functional bowel disease which has the highest incidence. Its risk factors include intestinal flora imbalance, intestinal bacterial overgrowth, intestinal motility disorders, visceral hypersensitivity, abnormal intestinal secretion and absorption, intestinal barrier function damage, abnormal gut immune, abnormal brain-gut axis. Existing studies have found that the above pathogenic mechanism may be related to the intestinal flora imbalance, which will be reviewed in this article.