Abstract: For constructing the DNA vaccine, apair of specific PCR primers were designed according to the nucleotide sequence of Aeromonas hydrophila major outer membrane protein gene published by our lab previously. The PCR products were inserted into the eukaryotic expression vector pcDNA3 to construct a DNA vaccine named pcDNA3-POMP.SD rats were immunized with purified prokaryotic-expressed protein GST-POMP to make antiserum, whose antibody titer, measured by ELISA, was over 1∶100 000.293cells were transfected with pcDNA3-POMP, 48hours after transfection, the cells were collected for total RNA extraction and RT-PCR, and the expression of exogenous momp were detected.Therefore, we have constructed a plasmid of DNA vaccine for Aeromonas hydrophila, vaccination and evaluation of this DNA vaccine will be studied in the future.