Microecology is a science that studies the structure and function of normal microbial communities and their interdependence and mutual restriction with their hosts. It was first proposed by VolkerRush of Germany in 1977. After 30 years of development, microecological research has made great progress, among which the most important achievement is the wide application of microecological agents in clinic. Peking Union Medical College, located in Beijing, is a national key university directly under the National Health and Wellness Commission and implements a unified management system with China Academy of Medical Sciences. It is a national "double-first-class" university and was selected into the excellent doctoral education and training program.