Abstract: In order to realize the efficient expression of Toxoplasma gondii major surface antigen 1（SAG1） protein in the prokaryotic expression system, in the experiment, according to the Toxoplasma gondii SAG1 gene sequence in GenBank（accession number S76248.1） and codon preference of E. coli, the target gene sequence was optimally designed. The recombinant expression plasmid pET32a（+）-SAG1 was constructed with pET-32a（+） as expression vector and transformed into E. coli BL21（DE3） competent cells; the recombinant bacteria were induced with isopropyl-β-D-thiogalactopyranoside（IPTG） to express the recombinant protein. Large amount of recombinant protein was expressed by optimizing the induction conditions; the recombinant protein was purified by the NGC^TM chromatographic purification system. And the recombinant protein was identified by Western-blot using monoclonal anti-HIS tag antibody and Toxoplasma gondii positive serum in dogs as primary antibody respectively, and sheep anti-mouse IgG-HRP and HRP-rabbit anti-dog as secondary antibody. The results showed that the recombinant expression plasmid pET32a（+）-SAG1 showed one vector band and one target gene band at 5 900 bp and 1 020 bp, respectively, which were consistent with the expected results. The recombinant protein was 55 ku in size and was successfully expressed as inclusion bodies, and the highest expression of recombinant protein was achieved when the induction conditions were 25 ℃ and 0.4 mmol/L IPTG for 8 h. The purified recombinant protein had a single band and high purity; the mass concentrations of the three samples were 0.409 5, 0.368 5, and 0.451 9 mg/mL, respectively. The expressed recombinant protein specifically bound to both anti-HIS tag monoclonal antibody and Toxoplasma gondii positive serum in dogs. The results suggested that Toxoplasma gondii SAG1 recombinant protein was successfully expressed in E. coli, and the purified recombinant protein had high purity and mass concentration with good reactivity.