¡¾Abstract¡¿ AIM: To construct R9/ScFv14/EGFP fusion genes and to analyze the binding activity of the fusion proteins after they were expressed in E.coli BL21. METHODS: A series of oligonucleotide primers were designed and used to amplify the genes of ScFv14 and R9/ScFv14. The PCR products were cloned into pMD18ª²T vector, followed by DNA sequencing. R9/ScFv14 gene and ScFv14 gene were ligated with EGFP gene respectively before they were recombined into the expression vector pET32a. After induced in E.coli BL21 by IPTG, the expressed fusion proteins named R9/ScFv14/EGFP and ScFv14/EGFP were detected by SDSª²PAGE and the binding activity of them were analyzed by indirect ELISA. RESULTS: Restriction endonuclease digestion and DNA sequencing proved that the two fusion genes were correctly constructed. SDSª²PAGE analysis showed that they were successfully expressed in E.coli BL21 and the percentages of them were 20% and 25% of total bacteria proteins respectively. Indirect ELISA confirmed that the expressed products had antigen specific binding activity. CONCLUSION: The two fusion genes were constructed successfully. And the products of them expressed in E.coli BL21 maintained the binding activity to HBsAg. ......