Abstract: A strain of gram-negative bacteria, named HM2, was isolated from the liver of a diseased Anguilla marmorata. The LD50 of 96h was 9.98107CFU/mL. HM2 was identified as Klebsiella pneumoniae according to its culture specific and physio-biochemical characteristics as well as ATB Expression systematic identification. By using the general primers of 16S rRNA, the gene fragments were amplified by PCR with a size of 1393 bp (GenBank No. JX282908). The amplified gene was sequenced and compared with those related sequences in GenBank and the phylogenetic tree was constructed on the basis of the sequencesof 16S rRNAs. The BLAST result showed that HM2 had the highest homologies (100%), with sequence of K. pneumoniae, and the phylogenetic tree result revealed further that this strain clustered together with K. pneumoniae. On the other hand, the results of artificial infection experiments revealed that HM2 had a strong ability of the diseases induction. By testing with twenty antimicrobial agents, HM2 was found to be with high sensitivity to imipenem, streptomycin and amikacin; while it was resistant to seventeen other antimicrobial agents, including ampicillin, amoxicillin-clavulanic acid, cefalotin, ceftriaxone, cefotaxime, cefoxitin, sulfonamides, trimethoprim-sulfamethoxazole, rifampin, nalidixic acid, ciprofloxacin, norfloxacin, ofloxacin, nitrofurantoin, tetracycline, doxycycline and chloramphenicol. The guidelines for the rational use of drugs are urgently needed to prevent the progress of antimicrobial resistance in aquaculture in future.