Objective To explore the effectiveness of passive immunization of fetus via mother on preventing the transmission of HBV from mother to infant. Methods A prospective randomized controlled study was designed. Fifty-two HBeAg positive pregnant women were randomly allocated to two groups, of which 28 women were allocated to trial group, and injected with 200 IU of hepatitis B immune globulin (HBIG) for 1 injection at the 28th, 32nd and 36th weeks of pregnancy respectively, 24 women allocated to control group were given no injection of HBIG. The samples of cord blood from the newborns in two groups were collected and tested for HBeAg and HBV-DNA by ELISA and FQ-PCR. Results The rates of HBeAg positive in the newborns were 21.4% in trial group, 79.2% in control group. There was statistically significant difference between two groups ( χ2=17.26, Plt;0.01, RR=0.27). The rates of HBV-DNA positive in newborns were 25.0% in trial group, 83.3% in control group, showing statistically significant difference between the two groups (χ2=17.62, Plt;0.01, RR=0.30). In the trial group, there were 21 newborns with HBV-DNA negative, 7 with HBV-DNA positive. HBV-DNA quantities were significantly lower in 7 newborns than in their mothers (T=28, P=0.02, Wilcoxon test). Conclusions Multiple injections of HBIG to pregnant women with HBeAg positive before labor could greatly reduce mother-infant transmission of HBV.