A pathogenic bacterium was isolated from the ascites,liver,spleen and kidney of the diseased snakehead (Channa argus) with visceral sarcoidosis from Meishan,Sichuan Province.Morphologic structure,dyeing observation,physiological and biochemical tests,PCR amplification of 16S rRNA gene and special sequence of the isolate were applied to determine the pathogen,and then drug sensitivity test was also carried out.The results showed that the isolate was similar to Nocardia in morphological and biochemical properties.The results of PCR amplification,sequencing and phylogenetic analysis of the 16S rRNA gene showed that the pathogen had close genetic relationship and maximum homologies with Nocardia,having a distant sequence similarity more than 99% with N. seriolea. Moreover,the bacterium was identified as N. seriolea by PCR amplification with special primers N5F1/N5R1.Besides,the results of drug sensitive test indicated that the organism was sensitive to Tetracycline,Doxycycline,Minocycline,Azithromycin,Sulfisoxazole and Rifampicin.