To identify genes that are differentially expressed, we compared the mRNA expression profile of Harmonia axyridis larvae untreated and treated with LPS. We extracted mRNAs from the larvae with or without LPS treatment, and subjected them to ACP RT-PCR analysis using a combination of 120 arbitrary primers (ACP1-ACP120)and oligo (dT) primer (dT-ACP2). After synthesized cloning DNA from 37 DEGs, it practiced the sequencing homology analysis using BLAST search. Among the 37 DEGs differentially expressed, we identified a cDNA showing homology with previously reported antimicrobial peptide. A cDNA encoding a 82-mer propeptide was identified and its predicted molecular mass and pI was 9.25 kDa and 7.54, respectively. A 35-mer mature peptide was also selected and named herein as Hamoniasin. The antimicrobial activity of chemically synthesized peptide (Mou def 1~8) against human bacterial pathogens was investigate. the result showed all bacteria strains were susceptible to Mou def 2,8 with MIC values in the 32 uM range. And biological changes of the respective cells according to peptide (Mou def 8) treatment were compared. MTT assay was tested that treatment of Mou def 8 decreased cell viability in AML-2, Jurkat, U937 (maximum 200ug/ml, 24hours). That is, fragmentation of DNA, typical characteristics observed in the process of apoptosis, was confirmed in the nucleus of cells dying owing to Mou def 8 treatment.