Abstract: Fifteen strains of fish pathogens were tested for their sensitivity to 17different antibacterial agents and the detected drug resistant strains were investigated todetermine if they possessed R plasmids.These pathogens included A.hydrophila,Vibrio, E.tarda, Yersinia and Pseudomonas.Most of them were resistant to β-Lactamsand erythromycin.All of tested strains were sensitive to tobramycin.The transferableR plasmid pWH9601 was detected from a strain of A.hydrophila CJ26.The detectedR plasmid showed resistance to tetracycline and sulfonamides.Resistance totetracycline conferred by pWH9601 was inducible in E.coli K-12 after exposure to1.0ug of tetracycline Per ml.This plasmid can transfer tO E.coli K-12 RC85 from A.hydrophila CJ26 within 0.25h at 37℃ by bacterial mating .This transfer can occur at12℃.