Abstract: OBJECTIVE To explore the clinical influencing factors for vaginal group B Streptococcus (GBS) infection and its influence on maternal and infant prognosis. METHODS The vaginal secretions specimens were collected from 3 260 pregnant women who awaited for delivery in Qinghai Red Cross Hospital from Jan 2016 to Jan 2018, and the umbilical cord blood specimens were collected after they gave birth. The incidence rate of GBS infection, drug resistance and clinical influencing factors for GBS infection were observed. RESULTS A total of 98 strains of GBS were isolated, with the isolation rate 3.01%. The drug resistance rates of the GBS strains to chloramphenicol, erythromycin, levofloxacin and clindamycin were 100.00%, 89.80%, 71.43% and 30.61%, respectively. The BMI more than 28 kg/m², gestational diabetes mellitus (GDM), vulvovaginal candidiasis (VVC), delivery history and abortion history were the independent influencing factors for the GBS infection during the third trimester of pregnancy. The incidence rates of fetal membrane infection, perineal infection, premature delivery, neonatal pneumonia and intrauterine distress were significantly higher in the GBS-positive pregnant women than in the GBS-negative pregnant women after they gave birth (P<0.05). CONCLUSION The clinical influencing factors for the vaginal GBS infection include the body mass index, GDM, VVC, delivery history and abortion history. The vaginal GBS infection may lead to the increase of incidence of premature delivery, premature rupture of fetal membrane and neonatal pneumonia and result in severe maternal and infant prognosis. It is necessary to take targeted prevention and treatment measures so as to minimize the impact on the maternal and infant health.