This study aimed to investigate the clinical characteristics, distribution of different strains and risk factors of patients infected with Streptococcus anginosus group (SAG). In the population of 463 patients, the male-to-female ratio was 1.95:1, and the patient age ranged from 6 months to 103 years. There were 49 children (10.58%), 311 young and middle-aged adults (67.17%), and 103 elderly adults (22.25%). Approximately 45.4% had underlying conditions, which were mostly malignant tumors and diabetes. Of the 463 specimens, 254 were S. anginosus (54.86%), 173 were S. constellatus (37.37%), and 36 were S. intermedius (7.77%). According to the age distribution, the incidence peaked in the 35-54 year age group. Different sites of infection had statistically significant differences regarding the constituent ratios of these three species. Different age groups also exhibited statistically significant differences in constituent ratios of the pathogenic organisms, as well as organ infections. In our population, 269 were clinically cured, 184 reported satisfactory improvement, and 10 died. SAG, as an opportunistic pathogen, can induce pyogenic infections in patients of all ages and shows no significant gender predilection in any age group. The three pathogenic organisms had differences with respect to patient age and infections of body sites.