Objective To identify highly sensitive and specific antigens in Aeromonas hydrophila strain ATCC7966 by using immunoproteomics.Methods Outer membrane proteins were extracted from the Aeromonas hydrophila strain by using two-dimension electrophoresis and identified by LC-LTQ-XL-MS ( liq-uid chromatography coupled with linear ion trap mass spectrometry).Western blot assay was performed to screen out the immunogenic proteins.Results A total of 43 peptides representing 39 proteins were identi-fied by LC-LTQ-XL-MS.Among the 39 proteins, 69% were outer membrane proteins and 12% were inner membrane proteins.They were involved in the process of transportation, cell motility, biosynthesis, etc. One candidate vaccine antigen was identified by using two-dimensional Western blot analysis .Conclusion The immunoproteomics approach could be used to identify immunogenic proteins of Aeromonas hydrophila. This study provided references for further investigation on candidate vaccine antigens.