One strain of germ is isolated from the bacterial septicemia sufferer of silver carp. It is numbered as Qing 1 - 2 - 3- The bacterial septicemia artificially duplicated has succeeded by using germ Qing 1 - 2 - 3 infect the healthy individuals of silver carp. The morphology, nutrient demand, growth characteristic and biochemical reaction of the strain has been observed. lt is found the germ of Qing 1 - 2 - 3 is Aeromonas hydroPhila. The biochemical characteristic of Qing 1 - 2 - 3 is different to the pathogenic bacteria of allogynogentic crucian carp. It is indicated that Qing 1 - 2- 3 strain is a different strain of pathogenic Aeromonas hydrophila.