A bacterial pathogen strain MS315509 was isolated from the surface ulcer of the sick Micropterus salmoides (M. salmoides) in a perch farm in Liling City, Zhuzhou City, Hunan Province. The isolate was identified morphologically and molecularly as Aeromonas hydrophila. The results of artificial infection showed that the half lethal dosage of MS315509 in M. salmoides fry was 5.47 × 107 cfu/mL. The virulence gene detection showed that the strain MS315509 carried three virulence genes: cytotoxic enterotoxin(alt), excitatory enterotoxin(act) and adhesin(aha1). Drug susceptibility testing of strain MS315509 utilizing 12 antibiotics and 12 herbs showed that the strain MS315509 was highly sensitive to gentamicin, cefradine, Shiliupi, Sumu, Wubeizi, Hezi, and resistant to tetracycline, cefazolin, kanamycin, oxacillin, enrofloxacin, penicillin, vibramycin, streptomycin, Huanglian, Aiye and Shudihuang.