A pathogenic bacterial strain of B20200824 was isolated from the brain, spine, liver and kidney of diseased Pelophllax nigromaculatus. The strain was identified by physiological and biochemical assays, 16S rRNA sequencing and evolutionary tree construction, then the susceptibility and the minimal inhibitory concentrations of antibiotics were determined by disk diffusion and broth micro-dilution methods, respectively. After identification, the strain was found to be a Gram-negative short bacillus with biochemical characteristics consistent with those of proteus vulgaris. Moreover, 16S rRNA sequencing and phylogenetic results revealed that the strain had a close genetic relationship with proteus vulgaris, which shared over 99% genetic homology. Thus, B20200824 was identified as proteus vulgaris. The results of drug susceptibility test showed that the strain was resistant to norfloxacin, amoxicillin, enrofloxacin and other 3 drugs, intermediate to doxycycline and erythromycin, and susceptible to azithromycin, cefotaxime, florfenicol ant 2 other drugs. Similar results were obtained according to the results of the minimum inhibitory concentration assay.