Abstract: Widely exists in water and soil, Aeromonas hydrophila is a commonpathogen for human, livestock and fish. It was previously observed in our lab that the expression of the proteins associated with the fatty acid biosynthesis in A. hydrophilarose under the stress of chlortetracycline. But the specific properties and functions were not understood. Therefore, this study was designed to clone and express those potentially important proteins, including acetyl-coenzyme A carboxylase carboxyl transferase subunit alpha (AccA), acetyl-coenzyme A carboxylase carboxyl transferase subunit beta (AccD), 3-oxoacyl-acyl-carrier-protein synthase Ⅰ (FabB), and malonyl coA-acyl carrier protein transacylase (FabD) for further investigation. By comparing the survival rates of high-expression strains of A. hydrophila under chlortetracycline stress, the drug-resistance relating to the proteinsin the fatty acid biosynthesispathway was analyzed. The results showed that the high-expression proteins, AccD, FabB and FabD, could indeed significantly increase the survival rate of the pathogen under chlortetracycline stress, while AccA did so only during the initial stage. Consequently, a critical role of these proteins involving the bacterial drug-resistance was clearly demonstrated. With the finding, further study to unveil the mechanism of antibiotic-resistance of the pathogen is in order.