The present invention relates to DNA constructs that can produce antimicrobial materials efficiently from microorganisms and the preparation method thereof. The present invention also relates to the useful vector for the DNA construct. The DNA construct according to the present invention comprises a first gene coding for entire, a part of or a derivative of purF gene and a second gene coding for antimicrobial peptide. According to the present invention, antimicrobial peptides can be mass-produced by the following steps: preparing an expression vector containing a DNA construct comprising a first gene coding for an entire, a part of or a derivative of purF gene and a second gene coding for antimicrobial peptide; transforming the bacterial host cells with the above-mentioned vector, culturing the transformed cell to express the above-mentioned DNA construct; and recovering the above antimicrobial peptide.