Abstract: The exotoxin ApxⅠ, ApxⅡ and ApxⅢ of Actinobacillus pleuropneumoniae was expressed in E.coli, the recombinant protein was purified and mixed with A.pleuropneumoniae serotype 7, which is prevalent in China, then emulsified with Freund’s incomplete adjuvant in equal volumes to get a sort of mixed subunit bacterin. Groups of BALB/c mice were immunized twice at week 0 and 2,then challenged intraperitoneally with serotype 1 and serotype 7 at week 4. Antibodies were detected with ELISA and IHA. After second immunization, antibody level increased obviously and the immune protection rate against serotype 1 and serotype 7 reached 83.3％ and 91.7％ respectively, challenge strains were reisolated from dead mice. These preliminary results showed that this mixed subunit bacterin had good protection against homologous and heterologous A.pleuropneumoniae，which built a good foundation for the further research of high efficacy vaccine against porcine pleuropneumonia.