Two vibrio sp. strains were isolated from disease catfish(silurus asotus). The present isolates were identified as Vibrio ordalii based on their biological and biochemical characteristics; they were positive for acid production from glucose, Iactose, maltose, sucrose and salicine. while negative for arabinose. galactose, inocitol and xylose. They are named KL-1 and KL-2, KL-1 and KL-2 strains were similar to physiological characteristics: growth was observed at pH 5 to 10 and in 0% to 6.0% NaCl. Two strains did not growth at a concentration above 7.0% NaCl and pH10. This bacterium was infected into health catfish hypodermically. Such injection was found to induce haemorrhagic ulcers very similar to those observed in naturally infected fish. At 24h post-infection, the red spot developed around the injection site and grew bigger to from a red sport area. At 120h post-infection, the muscle ncerosis was extended near the ventral fin. The seventy percent lethal dosage was appeared to water temperature at 25℃. Two strains were tested for drug senistiveity by plate method. KL-1 and KL-2 strains were sensitive to GM. K, N, S and SxT, but resistant to CF. L and VA