Abstract: Objective To explore the relationship of TLR3 in placenta and hepatitis B virus infection in pregnant women through comparing the difference of TLR3 mRNA expression and protein distribution in normal and HBsAg positive pregnant women.Methods 157 placenta of normal and HBsAg positive pregnant women were collected.Expression of TLR3 mRNA was analyzed by reverse transcriptase PCR(RT-PCR).Localization of TL R3 protein expression in placenta was analyzed with immunohistochemistry ABC technology.Results RT-PCR revealed that TL R3 decreased in gene levels in HBV infection women's placenta(t=3.003,P<0.05).Expression of TLR3 protein in paraffin-embedded placenta tissue indicated expression was lower in HBV infection women than in normal women(χ²=5.641,P<0.05).TL R3 protein can be expressed on all section of placenta.Conclusion The down-regulation of TLR3 associates with HBV infection in pregnant women.TLR3 perhaps can effectively protect placenta from HBV infection(OR=0.733,95%CI=0.656～0.818).