Abstract:Nurturing numerous microorganisms,oral cavity is the window into the physiological functions of the body.Oral microbiota is a mirror of the interaction between the host and environmental factors,which influences human health and disease progress.As the early colonizers of the oral cavity,the symbiotic Streptococcus and Veillonella contribute to the development of biofilm in human oral cavity.Mounting evidence suggests the key role of the symbiont in the development of many oral disorders,such as dental caries and periodontal disease.In certain state,they can also break through or invade the digestive barrier to colonize in remote organs,thereby affecting human health.They have been used as potential biomarkers for the occurrence,development,and prognosis of many systemic diseases.Thus,this paper reviewed the pathogenic mechanism of the Streptococcus-Veillonella symbiont,analyzed the characteristics of them in the microecosystem related to common systemic diseases,and proposed the representative diagnostic combinations,which would be expected to lay a scientific basis for the diagnosis and prevention of systemic diseases.