A bifuctional anti-HBsAg-alkaline phosphatase fusion protein expression vector pHBFAP was constructed by attaching the PCR cloned E.coli alkaline phosphatase gene to the C-terminal of the anti-HBsAg Fd fragment gene. E.coli XL1-Blue was transformed with pHBFAP, and induced with IPTG. The HBsAg banding ability and the alkaline phosphatase catalytic activity were detected by using ELISA in the induced bacterial supernatant thus indicating that the anti-HBsAg-alkaline phosphatase bifunctional antibody was expressed successfully in E.coli.