Aquatic animal cases are collected from cultured fish farm in Taiwan. Techniques of culture, ioslation, API biochemical kit and cloning of sequence of 16S RNA are carried out for diagnosis of bacterial diseases. On the other hand, diagnosis and surveillance of viral diseases are done by utilizing the cell culture and PCR method. The data of disease prevalence can provide reference of vaccine development and prevention policy, also resolving the problem of aquatic animal diseases for fish farmers.