Abstract: Vibrio anguillarum is a familiar pathogen of marine fishes, which express a kind of specific iron-uptake system when infection. The iron-regulated outer membrane proteins (IROMPs) of Vibrio anguillarum have been learned for its expression and composition, but not for the immune efficacy on fish yet. The immunoreactivity of outer membrane proteins (OMPs) and IROMPs of Vibrio anguillarum L-18 were analyzed with Western-blot in this study, and the difference of immune efficacy of OMPs and IROMPs was determined through immunizing flouder Paralichthys olivaceus. We found that the growth and the output of siderophore of L-18 were associated with the concentration of 2, 2’-dipyridyl (a kind of iron chelator) in media TSB. 100~130μmol·L-1 2, 2’-dipyridyl in TSB was affirmed to be the most proper iron-restricted condition, in which the growth of L-18 hadn’t been restrained strongly and the output of siderophore had reached to the tiptop. Under this iron-restricted condition, L-18 expressed 74.3ku and 77.4ku IROMPs. The 77.4ku protein, which was considered to be a important antigen, showed immunoreactivity clearly in Western-blot analyse. After immunization through intraperitoneal injection for 7 weeks , the cumulative mortality of P. olivaceus showed different values among formalin-killed whole-cell vaccine group, OMPs group and IROMPs group. The relative percent survival (RPS) of IROMPs vaccine reached to 75.9%, higher than 51.8% of OMPs vaccine significantly. The antibody titre of IROMPs group advanced significantly compared with OMPs group, nearly the same as the whole-cell group, but the survival index (SI) of it in serum had no obvious change. Key words： Vibrio anguillarum ; IROMPs ; Paralichthys olivaceus