ALFPm3 is nature peptide of main antimicrobial peptide family (Anti-lipopolysaccharide factor) in shrimp. Also, the ALFPm3 peptide involved in capable of antifungal and antiviral activities. In this study, the authors cloned and expressed ALFPm3 gene from Vietnam shrimp (Penaeus monodon). Obtained ALFPm3 gene is 372 bps lengths, coding for 123 amino acids. Alignment of the newly determined sequence and the best homologous sequence in GenSank showed that there are 4 different nucleotides: 21 A - G, 26 T - C, 52 C - G, 120 A - G, resulted in 2 amino acid substitutions 9L - P and 18L - V that located in the signal peptide sequence. The cloned sequencewas submitted to GenSank with accession number JQ256520. ALFPm3 cDNA segment encoding mature peptide was expressed in yeast Pichia pastoris X33. Recombinant ALFPm3 in culture exhibited antibacterial activities against B.megaterium and E.aerogenes. The obtained result is the basis for functional investigation for application in shrimp disease prevention and treatment.