Abstract: ObjectiveThe triple microencapsulated oral vaccine was prepared to defend against hemorrhagic sep-ticemia disease of Monopterus albus, in order to promote development of M. albus aquaculture industry. MethodUsing Aeromonas hydrophila, Citrobacter freundii and Aeromonas sobria as antigens and sodium alginate as shell-material, the triple microencapsulated oral vaccine was prepared with emulsification method , and healthy M. albus were intragastrically immunized with the triple microencapsulated vaccine added into the basic diet, and booster immunization was conducted, then the immune indexes were determined. After 15 days of booster immunization, three alive strains(1.0×109 CFU/mL) were injected to enterocoelia of M. albus, so as to determine immune protective rate of triple microencapsulated oral vac-cine. ResultThe average particle size of prepared microencapsulated vaccine was 44.5 μm, and the average bacterial content was 4.56×109 CFU/mg. After taking orally triple microencapsulated oral vaccine of 0.4 and 0.6 g/kg, the superox-ide dismutase(SOD) activity, acid phosphatase(ACP) activity, alexine C3 content in serum of M. albus were signifi-cantly higher than those in control group(P<0.05), and the corresponding average antibody titer in serum were 7.5949 and 11.0651, respectively, the corresponding immune protective rates were 60%and 65%, respectively. All the indexes of M. albus in 0.6 g/kg dosage group were higher than those in 0.4 g/kg dosage group. ConclusionThe triple microencapsu-lated vaccine can improve the activities of SOD and ACP, and stimulate production of alexine C3, it is effective to help M. albus to defend against hemorrhagic septicemia disease induced by A. hydrophila, C. freundii and A. sobria. Further-more, booster immunization should be conducted, and dosage should be increased properly in aquaculture.