One strain Yg1 was isolated from the kidney of diseased Selenotoca multifasciata.The healthy Selenotoca multifasciata could be infected through artificial infection by these bacteria.The symptoms in artificially infected fish were similar to those infected naturally.The characters of re-isolated strains were the same as the initially isolated strain,which was identified as Streptococcus iniae by the means of ATB system，morphological, physiological and biochemical tests, and 16S rRNA sequence analyses.The pathogens were sensitive to the following antibiotics: enrofloxacin, oxytetracycline, roxithromycin, doxycycline, tetracycline, levofloxacin.