Abstract: Small intestinal bacterial overgrowth(SIBO) is defined as bacterial overgrowth in small intestine caused by abnormal increase in the number of intestinal bacteria and(or) changes in bacterial species. The etiology of SIBO is complex. Anatomical abnormalities, small intestinal motility disorders, inadequate gastric acid secretion and abnormal protective antibacterial mechanisms may lead to SIBO. SIBO has a high positive rate in functional gastrointestinal disorders, inflammatory bowel diseases, liver cirrhosis, chronic pancreatitis, metabolism syndrome, systemic cirrhosis and other diseases, which indicates that intestinal bacteria play a certain regulatory role in many diseases. This review aims to summarize the research progress of SIBO and its associated diseases.