Abstract: From January to April of the year 2006,in cultured Apostichopus japonicus broke out skin ulcer syndrome in several areas nearby Qingdao,whose typical clinical signs were mouth swelling,eviscerating bowels,skin ulcer,body disjointing and then the infected sea cucumber died.Bacterium 060330B was isolated from focus tissue of Apostichopus japonicus,whose predominance degree reached 90% and was verified to be the pathogen causing skin ulcer syndrome based on artificial infection test.Morphological observation,semi-automatic identification through API system as well as traditional physiological and biochemical methods were applied in the bacterial classification.The results showed that 060330B had same character as Pseudomonas genus bacteria,its characteristics were similar with Pseudomonas putida,having short rods with several polar flagella,forming green colony on TCBS agar.Further results from 16S rRNA sequence analysis turned out that the sequence of 060330B was highly identical to Pseudomonas putida,with 99.5% identity.Thus bacterium 060330B was identified as Pseudomonas putida,and regarded as one of the pathogens causing skin ulcer syndrome of cultured Apostichopus japonicus.In addition,epidemiology investigation and detection of several samples from different areas revealed that the ponds whose culturing history reached two years or more and having thick black bottom mud with fishy smell were likely to result in the outbreak of skin ulcer syndrome in cultured Apostichopus japonicus at that time.