Abstract: A highly pathogenic bacterium WSQ-01 was isolated from the diseased Oxyeleotris marmoratus with typical skin ulcer. The bacteria strain was a gram-negative bacillus whose colony was white，round and smooth edges. The 16S rRNA of the bacteria was amplified，cloned and sequenced. The sequence were Blast in GenBank and downloaded the high homology bacterial sequence，then the sequences were aligned，analyzed and constructed the phylogenetic tree. The similarities of the 16S rRNA gene sequences in the strain WSQ-01 to other Aeromonas veronii were more than 99%. According to the phylogenetic tree，the strain JX-096 clustered together with Plesiomonas shigelloides. Animal experiments confirmed that the bacteria can cause skin ulcer and death on health Oxyeleotris marmoratus and have a strong pathogenic effect. Sensitive test of the bacteria showed that the strain highly sensitive to tetracycline，doxycycline，erythromycin，florfenicol，rifampicin，ceftazidime，ofloxacin，levofloxacin and enrofloxacin but resist to amamicin，streptomycin and amoxicillin.