In recent years, cultrued Scallop (Patinopecten yessoensis) died on a large-scale in seas near Changhai Xian.The abscess on adductor muscle is the main symptom.The artificial transmission experience indicated that a bacterium isolated from natural infected focus, named J6 displayed intense pathological activity to scallops, and the symptom is the same to natural intestion.The dose-and temperature-dependent test indicated that the bacterium had the most pathogenidty at 19℃ while the concentration was 1.09 × 105cuf/ml.The bacterial identification test through morphological specificity, physical and chemical properties and 16SrRNA gene sequence analysis showed the bacterium is Vibrio chagasii.