Coral reef ecosystems have the highest biodiversity on the earth, providing food for over 500 million people. But they have been strongly reduced due to the natural and human impacts. In particular, the disease is also one of the main factors are affecting coral reefs in worldwide. Determination the cause of coral disease still faces many difficulties. Characteristics of bacterial community on coral species in healthy status are standards for comparation with disease status in order to identify coral pathogens, especially when environmental conditions undisturbed. Therefore, characteristics of bacterial community in mucus of 12 coral species in coast of Long Chau and Cat Ba islands (Vietnam) have been studied. Molecular methods such as SYBR Gold staining, flow-cytometry, biolog ecoplate and denaturing gel electrophoresis were used. The research results and scientific basis were analyzed showed that there were many specific characteristics of the bacterial communities in coral mucus and there was a big difference when compared to the surrounding environment, and this will be standards for the determination of coral pathogens in the future studies.