Abstract: The aim of this experiment was to construct prokaryotic expression vector of reindeer βdefensin1(reBD1), induce the expression of reBD1 fusion protein in E.coli, and evaluate the bioactivity of the expression products. The prepropeptide of reBD1 was amplified by RTPCR. The mature peptide of encoding reBD1 was amplified from recombinant cloning vector PMD19T/reBD1, and then cloned into pET32a(+), in which reBD1 fusion protein expression was induced by IPTG in E.coli BL21(DE3). The expressed product was further cultured and purified for experiment of bacteriostasis in vitro. The results showed that the amplified products of prepropeptide and mature peptide were 215 and 138 bp, respectively, and the homology of the sequences of the targeted gene and reBD1 mRNA was up to 100%. The molecular weight of fusion proteins of prepropeptide and mature peptide were 28 and 24 ku.The agar diffusion method has demonstrated that 0.08 mg·mL-1 purified mature peptide protein has obvious antimicrobial activity against S. aureus and E.coli. From the results we can conclude that the prepropeptide and mature peptides have high expression level in E.coli, and the mature peptide has resistance to both Gram negative and Gram positive bacteria.