Abstract: A novel antibacterial agent, ethyl N-1-oxo-2, 4-hexadien-1-yl-L-phenylalaninate was synthesized.Excellent synthetic yield were studied through optimization of the conditions, such as reaction time, temperature and the ratio of L-phenylalaninate and SOCl2.When the reaction time was 3.5h, the reaction temperature was 60℃, the ratio of L-phenylalaninate and SOCl2 was 1∶3.2, the synthetic yield of L-phenylalaninate ethyl ester hydrochloride could reach 93.8%.The antimicrobial activity of ethyl N-1-oxo-2, 4-hexadien-1-yl-L- phenylalaninate against Escherichia coli, Bacillus subtili, Staphylococcus aureus the mixed bacteria from rancidity milk was studied and its minimum inhibitory concentrations of ethyl N-1-oxo-2, 4-hexadien-1-yl- L-phenylalaninate against these bacterial strains were 2.50, 0.75, 2.00 and 2.50mmol/L respectively.Its antibacterial activity was much better than sorbic acid.At the same time, ethyl N-1-oxo-2, 4-hexadien-1-yl-L-phenylalaninate still exhibited good antibacterial activity in alkaline condition.The growth adaptation period of the mixed bacteria from rancidity milk could be prolonged to 36h.