In the process of biological evolution, microorganisms and their hosts (humans, animals, plants and microorganisms), microorganisms and microorganisms and between them and the environment, as a result of long-term mutual adaptation, under normal circumstances, the biological host of the body surface and the body of the distribution of a certain species and number of specific microbial groups to form an ecosystem and to maintain the ecological balance, known as the normal flora (Normal Flora) Normal Flora. Normal flora is distributed on the human body surface and with the outside world connected to the cavity, the distribution of parts of the skin, the respiratory tract, the external auditory canal, the digestive tract (oral cavity; stomach; jejunum; ileum; colon), the nasal cavity, the genitourinary tract, etc., which is the most intestinal tract. These microorganisms have formed a symbiotic relationship with humans over a long period of evolution. Many microorganisms are not only harmless, but also beneficial to humans. Normal flora in the intestinal flora is the most representative, the most effective research. The total number of intestinal flora can be up to 1014 bacteria, for the total number of human cells 10-20 times, including at least 14 genera (bacillus, bifidobacteria, lactobacillus digestive cocci, digestive streptococci, enterococci, enterobacteria, etc.), about 400-500 kinds of bacteria, 90% to 99.9% are anaerobic bacteria (bifidobacteria, lactobacilli, etc.), enterobacteria, enterococci, such as the number of aerobic bacteria are very small. Normal flora have many important physiological functions: 1, such as the antagonistic effect of the biology between the flora, the normal flora in the human body in a particular place of adhesion, colonization and reproduction, the formation of a layer of bacterial membrane barrier. Through the antagonistic effect, inhibit and exclude the invasion and swarming of passing flora, adjust the balance between the human body and microorganisms.2, immune effect, normal flora can stimulate the host to produce immune and clearance function.3, detoxification effect, such as bifidobacteria can make the intestinal tract excessive gram-negative bacilli down to the normal level, reduce the absorption of endotoxin.4, anti-tumor effect, can degrade, remove the body’s oncogenic factors. Activate the anti-tumor cytokines in the body, etc. 5, anti-aging effect. In addition to the above functions of the intestinal flora, the human body also has a nutritional role, the normal microorganisms of the human intestinal tract, such as bifidobacteria, Lactobacillus, etc. can synthesize a variety of vitamins necessary for the growth and development of the human body, such as B vitamins (vitamins B1, B2, B6, B12), vitamin K, niacin, pantothenic acid, etc., but also the use of protein residues to synthesize non-essential amino acids, such as aspartic acid, alanine, valine and threonine, etc., and participate in the metabolism of sugar and protein, while also promoting the absorption of iron, magnesium, zinc and other mineral elements. Lou Jin, Department of Gastroenterology, Children’s Hospital Affiliated to Zhejiang University School of Medicine Microecology is the study of the structure and function of normal microorganisms in the human body and their interrelationships with their hosts, and it is an important part of life science. The earliest microecology was proposed by Volker Rush of Germany in 1977, and after 30 years of development, microecology research has achieved long-term development, in which the wide application of microecological preparations in the clinic is one of the important achievements in the development of microecology. Microecological preparations, also known as probiotics, are preparations prepared by utilizing normal microbial members or substances promoting microbial growth, which can achieve the purpose of preventing and controlling diseases and promoting health by adjusting or maintaining microecological balance. According to the material composition of microecological preparations can be divided into probiotics (Probiotics), prebiotics (Prebiotics), synbiotics (Synbiotics) three categories. Probiotics are live bacteria and their metabolites that improve the micro-ecological balance of the host and play a beneficial role in improving the host’s health level and state of health. Probiotics exist in all corners of the earth, and the beneficial bacteria or fungi in the body of the animal are mainly: lactobacilli, bifidobacteria, actinomycetes, yeasts and so on. A prebiotic is a non-digestible food ingredient that selectively promotes the activity or growth and reproduction of beneficial intestinal flora to promote host health and growth. The first prebiotics discovered were bifidogenic factors. Later it was discovered that a variety of indigestible oligosaccharides can be used as prebiotics. The most common oligosaccharides are lactulose, sucrose oligosaccharides, cottonseed oligosaccharides and oligomaltose. These oligosaccharides are not decomposed and utilized by harmful bacteria, and can only be utilized by beneficial bacteria to promote the growth of beneficial bacteria and achieve the purpose of adjusting the flora. In recent years, China’s research found that some Chinese herbal preparations can also be used as prebiotics. Probiotics have many advantages, there is no technical difficulties in maintaining the number of live bacteria, strong stability, long validity period, not only to promote the growth of beneficial flora, but also to improve the immune function of the body. Synbiotics is a biological preparation combining probiotics and prebiotics, which is characterized by playing the role of probiotics and prebiotics at the same time. The application of this kind of preparation has a tendency to increase day by day.