In the study, the spaA gene was expressed in the prokaryotic expression system and the immunoprotective effects of the expressed products were identified. According to the spaA gene sequence of clinical isolates SG7 of Erysipelothrix rhusiopathiae, primers were designed to amplify the spaA gene without signal peptide, and then the spaA gene was connected to the expression vector pGEX-4T-1. The recombinant vector was transformed into BL21（DE3）cells of Escherichia coli, and the expression product was identified by SDS-PAGE after induction. The mice were immunized with spaA protein purified by GST affinity chromatography. The immunized mice were challenged with Erysipelothrix rhusiopathiae strain, the death number of mice was counted, and the immune protection rate was calculated. The results showed that the spaA gene of Erysipelothrix rhusiopathiae without signal peptide was successfully inserted into the expression vector pGEX-4T-1, and the recombinant vector was transferred into BL21（DE3） cells.The 97 ku target protein was successfully expressed after induction. The purified expression product could stimulate the good immune response of mice and provide complete protection against the infection of Erysipelothrix rhusiopathiae. The results can provide a reference for the development of Erysipelothrix rhusiopathiae spaA subunit vaccine.