〔Abstract〕 Objective To assess the epidemiological, drug resistance, and their relative risk and prevalence for yielding clinical diseases ofStreptococcus mitisgroup(SMG) bloodstream infections in recent years. Methods A total of 50 blood culture specimens were collected from patients with SMG bloodstream infection. These SMG isolates were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF MS). The susceptibility to antibiotics was tested by minimal inhibitory concentrations and Kirby-Bauer(K-B) disk diffusion methods. The data were comprehensively analyzed by statistical software combined with clinical data. Results Five strains were identified in SMG bloodstream infection by mass spectrometry, namelyStreptococcus oralis/mitis(S.oralis/mitis),Streptococcus pneumonia(S.pneumonia),Streptococcus gordonii(S.gordonii),Streptococcus sanguinis(S.sanguinis), andStreptococcus parasanguinis. These SMG showed high resistance to erythromycin and clindamycin, but low resistance to penicillin, ampicillin and ceftriaxone. Reduced hemoglobin and albumin, elevated C-reactive protein and procalcitonin were the common hematological changes in patients with SMG bloodstream infections. In SMG bacteremia,S.gordonii,S.sanguinisandS.orals/mitiswere the leading group causing infective endocarditis. Patients with myocardial disease factor were more likely to cause infective endocarditis byS.gordoniiandS.sanguinis, compared withS.orals/mitis.S.oralis/mitisbacteremia more occurred in patients with renal transplants progressing to pulmonary infection. Conclusion In this area, β-lactam antibiotics are the best choice for treating SMG. SMG species with closely related phylogenetically show different prevalence and risk of clinical disease in bloodstream infection patients. Early prevention and diagnosis of bacteremia caused by SMG are necessary for clinical diagnosis, treatment and effective control of infectious diseases progression.