To produce antibodies capable of neutralizing botulinum neurotoxin type B (BoNT/B), We cloned the carboxy-terminal end of Hc containing the major determinants responsible for specific toxin,induced and purifed. The heavy-chain and kappa light-chain variable region gene repertoire of immunoglobulin were amplified individually from the spleen cell mRNA by RT-PCR and joined as a single-chain Fv (scFv) DNA fragment. These fragment were cloned into the phagemid pCANTAB5E and the phage display library was constructed. Results showed that the high affinity scFv was obtained after 4 rounds of panning, with its DNA sequence conforming to that of mouse antibody.