Commensal viruses are widely involved in various physiological and pathological processes of the body,which have attracted highly attention in recent years.Commensal viruses play an important role in the development of autoimmune diseases,allergic diseases,tumorigenesis,antiviral immune response,and inflammatory diseases via regulating the development of immunocytes and the secretion of cytokines.With the development in high-throughput,next-generation sequencing technology and metagenomics,the research on commensal viruses and disease progression has further deepened people's understanding on the function of commensal viruses.Due to the differences of the distribution in the organism,the host genotype and the commensal microorganisms,the commensal viruses can produce many beneficial or adverse immune responses to the organism.This review focuses on the composition,function,mechanism of human commensal viruses and discusses the potential in disease diagnosis and treatment in the future.