Objective To explore the relationship between HBV-DNA load and the offspring vertical transmission of HBV.Methods 138 families who had taken the examination between August 2009 and November 2011 but the HBsAg of the housewife was negative,were chosen as research objects.Blood from the couples and sperms from the husbands during pregnancy were followed and collected for detection on related indicators.Cord blood was sampled after delivery for HBVM and HBV-DNA quantification.Those with HBV-DNA load ≥5 × 102 copies/ml were chosen as cases while those ＜5 × 102 copies/ml were formed as controls,respectively.Results 1) The positive rates of HBV-DNA was 34.8％ (48/138) in the neonatal cord blood while the positive rates of cord blood HBsAg and HBeAg were 28.3％ (39/138) and 15.2％ (21/138) respectively.2) The positive rate of semen HBV-DNA was 21.0％ (29/138) while the positive rates of paternal serum HBV-DNA and HBeAg were 76.8％ (106/138)and 42.8％ (59/138).3)Among the positive ones on paternal serum HBV-DNA,paternal serum HBeAg,semen HBV-DNA,items as measures taken for HBV vertical transmission and prevention on the fathers and the first class family histories on HBV appeared to be the risk factors for HBV paternal transmission (P＜0.05).4)Data from Multivariate analysis showed that positivities on patemal serum HBV-DNA,paternal serum HBeAg and semen HBV-DNA were risk factors for HBV paternal transmission (OR=5.7,95％CI:1.1-29.1 ; OR=4.2,95％CI:1.7-10.0; OR=6.7,95％ CI:2.4-18.9).5)Dose-response relationships were seen between levels of paternal serum HBV-DNA load and cord blood HBV-DNA load,between levels of paternal serum HBV-DNA load and semen HBV-DNA load,between levels of semen HBV-DNA load and cord blood HBV-DNA load.6)Results from the analysis on ROC curve showed that paternal serum HBV-DNA load level (105 copies/ml) and semen HBV-DNA load level (103 copies/ml)were better demarcation points to forecast the occurrence of paternal transmission of HBV,because of the better sensitivity and specificity they had.Conclusion Items as positives on paternal serum HBV-DNA,paternal serum HBeAg and semen HBV-DNA were risk factors for HBV paternal transmission.When paternal serum HBV-DNA load ＞ 105 copies/ml and semen HBV-DNA load ＞ 103 copies/ml appeared,the positive rate of HBV paternal transmission would increase.