Abstract: In this paper , a pair of primers were designed according to the nucleotide sequence of the ompII gene of Aeromonas hydrophila reported. With the specific primers , one target fragment about 1kb was amplified from the A . hydrophila genomic DNA via PCR. The target fragment was inserted into the linearized plasmid vector pRSET A. The nucleotide sequence of the inserted fragment , containing ompTS gene , was determined. The longest open reading frame (ORF) of 1068nt was identified and predicted to encode a 3552aa protein OmpTS with the molecular weight of 38. 9 kDa. Hydrophobicity analysis suggested that except for a potential 202amino2acid signal peptide , the protein was hydrophilic. The nucleotide sequence of ompTS gene showed 83. 5 % homology to the sequence of ompII gene. A Genbank search using the BLASTP program found that , the predicted amino acid sequence of the ompTS gene showed substantial identity with those of the outer membrane proteins reported in Escherichia coli , Klebsiella pneumoniae , Salmonella typhi , Serratia marcescens , Photobacterium profundum and Citrobacter freundii. Based on the amino acid sequence comparison , a high degree of amino acid sequence conservation at N2terminal was revealed. These analysis indicated that the ompTS gene is probably a novel structural gene that codes for OmpTS , which most likely forms pores in the outer membrane.