Old Li, who is over 60 years old, suffers from diabetes, chronic bronchitis and many other diseases, and uses many antibiotics all year round. In recent years, it is often accompanied by inexplicable gastrointestinal discomfort and diarrhea. The company’s main goal is to provide the best possible service to its customers. As we all know, in the normal human intestine there is a huge number and variety of microorganisms, these microorganisms are mainly bacteria, collectively known as the intestinal flora, the total number of up to 100 trillion, more than 1000 species. The relationship between the intestinal flora and the human body is intricate and complex, and is not yet fully understood, and it runs through various physiological activities and pathological processes in the human body, and has become an integral part of the human body. Under normal circumstances, the intestinal flora and the human body interdependence, mutual constraints, to maintain a dynamic ecological balance, once affected by the human body and external environmental changes, the balance will be broken, the formation of the destruction of physiological combinations, generate pathological combinations, which is the intestinal flora dysbiosis. The causes of intestinal flora dysbiosis are complex and diverse, including drugs, diet, age, abnormal intestinal dynamics and immune dysfunction. First of all, drugs, especially the long-term use of broad-spectrum antibiotics, can make the intestinal sensitive bacteria be inhibited, drug-resistant bacteria overproduction, which is the most common cause of intestinal flora dysbiosis. The old Li mentioned earlier developed the disease as a result. That is why antibiotics are classified as prescription drugs by the government and follow many norms in clinical use, just to avoid the abuse of antibiotics. Secondly, poor dietary habits, especially a high-fat diet, can disrupt the balance of intestinal flora. Therefore, it is important to adjust the dietary structure and develop good eating habits. Again, some studies show that the number of bifidobacteria in the intestine of the elderly significantly decreases, the number of enterobacteria and enterococci increases, and the intestinal colonization resistance decreases, which indicates that the intestinal flora changes with age. Therefore, the appropriate application of microecological agents, such as Bifidobacterium, Lactobacillus and Enterococcus, in diseases related to intestinal flora dysbiosis in the elderly is beneficial to the recovery of their health. Finally, when intestinal motility disorders and immune dysfunction occur, bacteria will be retained in the intestine for too long, secretory immunoglobulin A will be lacked, and intestinal bacteria will overgrow due to loss of monitoring, resulting in intestinal flora dysbiosis. In addition, such as trauma, severe infection, surgery, chemicals, mental illness, and tumors can lead to intestinal flora dysbiosis. The main manifestations of intestinal flora dysbiosis are diarrhea, which can be dilute watery stool, mucus stool or mucopurulent blood stool, abdominal pain, abdominal distension, intestinal rumbling, which can be accompanied by fever, nausea, vomiting, water-electrolyte disorder, hypoproteinemia, and shock symptoms in severe cases. Intestinal flora dysbiosis is closely related to a series of diseases such as Crohn’s disease, ulcerative colitis, irritable bowel syndrome, chronic hepatitis, fatty liver, liver cirrhosis, diabetes, and multi-organ failure. Therefore, correction of intestinal flora dysbiosis should be given sufficient attention, and clinical measures such as active control of underlying diseases, removal of causative factors, rational use of antibiotics, and application of microecological preparations should be taken to maintain the ecological balance of the intestinal flora. However, it is worthwhile to pay enough attention to the fact that microecological agents should also be applied reasonably, and excessive use may have the risk of secondary infection and spreading drug resistance.