AIM To determine the serumal type of a species of salmonella which was isolated from imported frozenlarge yellow croaker.METHODS Aseptically weigh 25 g gill and viscera of the fish into sterile wide-mouth 500 mL jar. Add225 mL sterile buffered protein broth (BP) and incubate 18 h - 24 h at 36℃±1℃. Gently shake incubatedsample mixture, and transfer 1 mL to 10 mL selenite cystine broth (SC), add additional 1 mL to 10 mLtetrathionate broth (TTb). Incubate 18 h- 24 h at 36℃±1℃. Streak 1 loopful of incubated SC on selectivemedia plates of DHL. Repeat with 1 loopful of incubated TTb and incubate plates 24 h at 36℃±1℃. FromDHL, pick with needle 3 typical Salmonella colonies-colorless with black centers. Inoculate Ktiger's Ironagar (KIA) and Lysine-motilify agar (LMA) for screening. Finally they are suggested to be Salmonella.Then apply biochemical and serological identification tests to 3 presumptive positive samples reexaminated byChina National Institute for the Control of Pharmaceutical & Biological Products and certified by WHO Collaborating Center for Reference and Research on Salmonella.RESULTS According to the biochemical reaction, accordance with the characteristics of Salmonella andthe ability to utilize malonate, duicitol negative, ONPG positive, KCN negative etc. the specialities can beprimarily determined as subgroup Ⅲ. Basing on the results of serological examinations it can defined as O50group. Its H antigen revealed a phase HZ66, Z57, Z68, but the another phase still remained undiscovered. The reexamining result of China National Institute for the Control of Pharmaceutical & BiologicalProducts (checking No. SJKS 961037): Through Gram stain, culture, biochemical and serologicalexaminations this bacterium remained unverified and suggested to send the specimen to WHO SalmonellaCentral Laboratory for checking up. WHO Collaborating Center for Reference and Research on Salmonella appraised this species as a newserumal type of Salmonella. diarizonde with serumal type 50:K:Zs7:Z68NT (checking No. 8687).CONCLUSION The species of Salmonella was certified to be a newly discovered serovar of Salmonella.