Abstract: Objective To observe the carriage of group B streptococcus (GBS) in pregnant women and its effect on the pregnancy outcome of the mother and fetus. Methods A total of 966 cases of late pregnancy women were as research subjects. Vaginal and rectal secretion of GBS were detected in all subjects. The carrying status of GBS were observed. The pregnancy outcomes of different groups were traced. The difference of pregnancy outcome between the maternal and fetal groups was analyzed statistically. Results The GBS infection rate of all 966 subjects in this study was 9.52%, and there was no significant difference in the rate of GBS infection among the subjects of different ages, abortion history and reproductive history (all P>0.05). The incidence of premature rupture of membranes, amnionitis, intrauterine infection, puerperium infection, neonatal infection, fetal distress and neonatal asphyxia were significantly higher in GBS positive group than in the GBS negative group (all P<0.05). The incidence of amnionitis, intrauterine infection, puerperium infection, neonatal infection, fetal distress and neonatal asphyxia in GBS positive intervention group were significantly lower than that of GBS positive group (all P<0.05). The incidence of amniotic inflammation, intrauterine infection and neonatal infection in GBS positive intervention group was significantly higher than that in GBS negative group (all P<0.05). There was no significant difference in the Apgar score, preterm delivery, cesarean section and postpartum hemorrhage between the three groups (all P>0.05). Conclusion GBS infection in pregnant women in late pregnancy can lead to premature rupture of membranes, amnionitis, intrauterine infection, puerperal infection, neonatal infection, fetal distress and neonatal asphyxia. The incidence of maternal and fetal adverse pregnancy outcomes is increased. The incidence of maternal and infant undesirable pregnancy outcomes can be reduced on a certain course and late pregnancy in the late pregnancy by the implementation of antibiotic prophylactic treatment. Prenatal GBS screening for pregnant women is of high clinical value.