Abstract: Objective:This study was designed to construct a expression vector for anti-HBsAg Fab fragment and interferon-aA（IFN-aA） fusion protein in E. coli.Methods:with PCR and molecular clone technique, the gene fragment of IFN-aA was introducedinto the corresponding endonuc-lease sites and artificial Linker at 5',3'termini, and then forming pHs/IFN-aA recombining it with the vector in correct endonuclease sites. Results:After checking with enzymic hydrolysis, the human gene of IFN-aA was correctly cloned to the vector, and the sequence of the gene was confirmed correct.Conclusion:The success in construction of human anti-HBsAg Fab fragment/IFN-aA fusion protein expression vector makes it possible to carry out further studies on expressing in E.coli and targeted therapy polypeptide for HB virus.