The aim of this study was to find an optimal preparation method of Photobacterium damselae subsp. piscicida vaccine for cobia (Rachycentron canadum). Various candidate vaccines combined with inactivated bacteria, extracellular products and Freund’s adjuvant were used to assay their efficiency against photobacteriosis by the safety trials and antibody response. The results showed that both inactivated bacteria and all extracellular products did not decrease the proliferation of gill cell. The best candidate vaccine was an admixture of inactivated bacteria of 8.4×109~1.7×1010 cells/fish (p < 0.05) and Freund’s adjuvant which produced high antibody titer from 1:416 to 1:960 during 29 ~ 35 days post-vaccination.