To determine the pathogenic bacterium infecting Siniperca chuatsi. Bacterium was isolated from the liver of diseased S. chuatsi and identified by the Vitek 2 Compact Identification System and 16S rRNA sequence analysis. Healthy S. chuatsi was used for experimental infection with bacterial suspension. A bacterial strain B01 was isolated from diseased S. chuatsi. Identification demonstrated that the bacterium was Pseudomonas fluorescens（Table1，Picture 2）, and it’s growth characteristics was aslo studied. And the results indicated the B01 could fluoresce under ultraviolet(Picture 1). Infection with the bacterial suspension to healthy S. chuatsi could reproduce the diseased symptoms as occurred naturally and the same bacterium could be recovered from these infected Siniperca chuatsi. The susceptibility test to antibiotics demonstrated that the bacterial strain B01 was susceptible to enrofloxacin, norfloxacin, streptomycin and tetracycline（Table2）. P. fluorescens is a pathogen for S. chuatsi.