Microorganism distributes in the organs of human body which connect with external environment, especially those organs in the gastrointestinal tracts, and it also plays a fundamental role in the physiopathology of the host's body. Because the microorganism is very small and has a great variety, it is difficult to reveal the significance of microorganism in the human physiopathology comprehensively and deeply. With the development of molecular biology, genomics, bioinformatics and other disciplines, the microbiome research will be more possible and easier. There are two key contents of microecology. One of these is to identify and quantify the diversity of microorganism, and the other is to reveal activity and the physiopathological function of microorganism in the host. Microbiome research methods, therefore, can be summarized as the traditional detection methods, construction of gene library, the genetic fingerprint analysis and molecular hybridization techniques and so on.