The intestinal microbiota has been the subject of large-scale research in recent years. The gut microbiota has been shown to co-evolve with us (Ley et al, 2008). The body produces more than 100 trillion intestinal microbiota which have a significant impact on the immune system, human physiology, metabolism and nutrition (Ley et al, 2006). The inability of the intestine to host the microbial cell community has been associated with intestinal diseases such as inflammatory bowel disease (IBD), encompassing ulcerative colitis, Crohn's disease, diabetes, obesity (Zhang et al, 2009) and malnutrition (Kau et al., 2011). It is also known as the hidden metabolic “organ.” The gut produces a diverse and complex microbial community that plays an important role in human health. It has been estimated that 1,000 bacterial species and 100 times more genes can be found in the human gut (Ley et al, 2006). The digestive tract of the newborn was sterile, the intestinal microbiota begins to colonize quickly after birth and continues its evolution throughout life. Enterobacter, Enterococci, Bifidobacteria, Clostridia, Streptococci are the first colonizers. The composition of the gut microbiota is unique in each individual, with little phylogenetic overlap between people. Even in twins, they share less than 50% of the species phenotype (Turnbaugh et al, 2010). It is shown that there is a stable microbial core within an individual, although this can be influenced by aging, diet, environment and health status (Qin et al, 2010). The gut microbiota plays an important role in human metabolism. Carbohydrates are important energy sources for human and microbial cells. Most complex carbohydrates and plant polysaccharides, such as cellulose, xylans, resistant starch, and inulin, cannot be digested by human enzymes. The intestinal micro......middle of paper......romental and genetic can also be the cause. Patients with type 2 obesity have been shown to have a different gut microbiota composition than a healthy control group, but it still remains doubtful whether altered gut microbiota is the cause of type 2 diabetes. . Larsen and his colleagues have recently carried out some impressive studies. They show that the composition of Firmicutes decreased while that of Bacteriodetes increased (Larsen et al, 2010). In conclusion, the gut microbiota plays an important role in human health and disease by affecting the host's metabolism and immune system. It contributes to human metabolism, physiology, immune system and nutrition. The intestinal microbiota evolves with us. Altered composition of the gut microbiota leads to many chronic gastrointestinal diseases. By various methods we can find out which microflora is harmful and brings benefit to the human intestine..