Immunoassay for determining aflatoxin B1 involves in using the toxic mycotoxin in a conjugated form. To replacing the toxic conjugate in an immunoassay, four mimotope peptides of aflatoxin B1 were acquired by a panning-elution selection from a phage library, and one mimotope peptide was fused with the major coat protein gVIIIp by the pC89 phagemid display system. It led to a high copy number expression of the mimotope peptide in a recombinant phage. The recombinant phage was identified by an anti-aflatoxin B1 monoclonal antibody, and confirmed by DNA sequencing. An immunoassay was set up with the recombinant phage. The new method was compared to a conventional immunoassay. The calibration curves and the results of accuracy and precision were almost identical in both methods, which demonstrated the possibility of using the recombinant phage replacing the aflatoxin B1-protein conjugate to set up immunoassay.