The invention discloses a labidura japonica de haan antimicrobial peptide DEI and application thereof in duck feed, and belongs to the technical field of bioengineering. The labidura japonica de haanantimicrobial peptide DEI is prepared by acquiring an antimicrobial peptide DEI of labidura japonica de haan, testing an amino acid sequence of the antimicrobial peptide DEI by using an automatic protein sequencing instrument, further by means of genetic engineering, designing a cDNA (complementary deoxyribonucleic acid) fragment of the amino acid sequence, establishing cloning plasmid pUC57-TM, converting escherichia coli DH 5alpha, performing PCR (polymerase chain reaction) and sequencing to carry out further identification, establishing a recombinant expression vector pPICZaC-TM, performinglinearization on the recombinant expression vector, performing electric conversion into pichia pastoris SMD1168, screening to obtain a high-copy recombinant yeast conversion factor, and culturing a single colony of the recombinant yeast conversion factor, thereby obtaining the labidura japonica de haan antimicrobial peptide DEI. The labidura japonica de haan antimicrobial peptide DEI can be applied to duck feed, then the immunity of ducks can be improved, the morbidity of the ducks can be greatly reduced, the survival rate of the ducks can be increased, and thus the feeding cost of duck farmers can be reduced.