Abstract: Objective To provide foundation for studying bispecific antibodies against HBV by genetic engineer ing.Methods Purifying the total RNA of the hybr idomas ag ainst HBsAg,amplifying the variable region of light chain(VL)and variable region of heavy chain(VH)by RT-PCR through the universal primers of the variable region of mouse immunoglobulin,ligating VL and VH fragments by a peptide linker(Gly4Ser)3,constructing ScF vinto pGEM-T Easy vector and analyzing its sequence by automatic sequencing.Results 414bp VL amplying fragment and 393bp VH product were obtained by RT-PCR,and 414bp of VL belonged to the family XX of K chain,393bp of VH belonged to the family IX of heavy chain.Conclusion The sequence of ScFv against HBsAg was successfully cloned.