Abstract: The human ant-i HBsAg ScFv and interferon gamma were connected with the linker to construct the ScFvIFNγgene by using overlap PCR techniques．The sequence of the ScFv-IFNγgene in the vector proved to be the same as the designed gene by sequencing．The ScFv-IFNγgene was successfully converted into the Pichia pastoris expression vector pPICZαA and transformed into Pichia pastoris X33．Screened strains were cultivated with methanol．Protein in the 42000of SDS-PAGE and WESTERN BLOT was obviously seen on the cultivated supernatant．The research has laid the foundation for further purifying interested protein as well as for raising the secretory expression level of interested protein．

Key words: overlap PCR, HBscFv-IFNγ, Pichia pastoris, secretory expression