Abstract: The international cooperated research projects of the Human Microbiome Project (HMP) and Metagenomics of The Human Intestinal Tract (MetaHIT) were officially launched in 2007, which indicated the era of metagenomics research of microorganisms in human gastrointestinal tract had been coming. Each human body is a superorganism which is composed of 90% commensal microorganisms, especially the intestinal microorganisms. The intestinal microorganisms play an important role on health maintenance since they are involved in the absorption and metabolism of nutrients in the human bodies. Herein, we review the research progress in the mechanism of intestinal microorganisms in human diseases. Our purpose is to provide novel ideas on human health and therapeutic targets of diseases.