Abstract: The pathogenic bacteria Vibrio harveyi discovered in abalone Haliotis diversicolor with withering syndrome is completely resistant to trimethoprim-sulfamethoxazole. This study identifies the resistance genes and their location in this bacteria′s plasmid. sulⅡ was detected in the plasmid with polymerase chain reaction. The conjugative transformation test shows that the plasmid is transferable and leads to the resistance of bacteria to sulfonamide. The complete sequence of the R plasmid is 10 940 bp long including 7 ORF which display biological function. sulⅡwas cloned into the multiple cloning sites pRSET-A(+) to build a recombinant positive plasmid. The SDS-PAGE indicates that the recombinant sulⅡ protein, in the form of inclusion body, is 31 kDa.