Abstract: To investigate the roles of two Cpx component systems in the growth and virulence of Aeromonas hydrophila, we constructed the cpxRA gene cluster mutant Δcpx with the deletion of 57—1879 bp using suicide plasmid pRE112 as the vector. This procedure was based on fusion PCR and gene homologous recombination principles. Through electrophoresis and fluorescence quantitative PCR, the partial deletion of the cpxRA gene cluster in the mutant was confirmed. Then we compared the differences between mutant and wild strains in biological characteristics including growth, biofilm formation, stress tolerance and virulence. The results showed that the mutant had no significant difference with the wild strain in morphology, growth, biofilm formation and virulence. The main differences existed in the response to high osmotic pressure, SDS (Sodium dodecyl sulfate), EDTA (Ethylene Diamine Tetraacetic Acid) and polymyxin B stimulation. This study reveals that the Cpx system of Aeromonas hydrophila is involved in the response to external stimulus factors, and plays a relatively minor role in virulence.