Germ-free animals and metagenomic technology are the two major wheels for the study of microbiome in human health.Without a transplantation model of germ-free animals inoculated with microbiota (bacterial strains),it is impossible to establish the causal relationship between microbiota and diseases.Without germ-free animals,there will be no rapid development of research on the relationship between microbiota and human diseases today and tomorrow.Application of germ-free animals has formed four kinds of general research models,including comparison of conventional and germ-free animals,bacteria (strain) transplantation with germ-free animals,rederivation of germ-free genetic engineering animals,and development of germ-free animals.Standardization of research mode will increase the scale and speed of application of germ-free animals.After ten years of efforts,Professor Wei Hong's group has built the largest scale,the most stable technical system,most widely used platform of germ-free animal in our country,which have provided a strong support in our country for scientific problem solving in the fields including animal husbandry,biomedicine,and food microbiology.At present,the germ-free animals are in small scale,low in efficiency,and the platform is separated from the application conditions.The basic theory and technical system of germ-free animals are still to be developed,and it is difficult to meet the growing demand for application.Establishment of an efficient large-scale research and application system of germ-free animals will meet the needs of rapid development of microbiome research in China.