Mass mortality of abalone Haliotis diversicolor aquatilis, occurred at abalone farms of Dongshan Prefecture, Fujian Province during the spring of 1999 and Since then pathological study was performed. Electron micrography revealed mass enveloped, about 100nm in diameter, hexagonal particles in the cytoplasm of liver of diseased abalone. Artificial infected experement revealed that the virus is the lethal pathogen of mass mortality, and histopathological changes and necrosis of the liver cell were the reshan of death. A further study on specib clasifieation of virus will be needed.