Small intestinal bacterial overgrowth can be diagnosed by breath test and endoscopic culture of small intestinal bacteria. Small intestinal bacterial overgrowth is a clinical manifestation of intestinal dysbiosis, which may be caused by prolonged stagnation of the small intestine, leading to overgrowth of bacteria, thus causing changes in the number and types of small intestinal bacteria. Some patients may show abdominal distension, abdominal pain, and some patients may not have any symptoms. Currently, the breath test is commonly used to confirm the diagnosis, which has the advantages of simplicity and ease of implementation, as well as high sensitivity and specificity. Bacterial culture of small intestinal fluid is the gold standard for the diagnosis of small intestinal bacterial overgrowth, because the examination needs to obtain some small intestinal fluid through endoscopy, and then carry out bacterial colony counting and culture, which is invasive and repeatable, and some of the bacteria are more special, and it is relatively difficult to culture them, so it is difficult to use them in clinic at present.