Objective:To acquire the purified recombinant lethal factor 253 (LF253)antigen which owned biological activity and test its competitive capacity binding protective antigen (PA)compared with lethal facfor (LF)protein. Methods:The LF253 gene was amplified by PCR,and the truncated LF gene was inserted into pET-28a (+),and transferred into E.coli.BL21 (DE3) as the host strain. LF253 was expressed as a recombinant protein induced with isopropyl-β-d-thiogalactoside(IPTG). The protein was purified with His label affinity chromatography and was subjected to antigenicity by Western blot and ELISA. The affinity was detected by Biacore T-100,and the biological activity was detected by cellular toxicity test. Results:We successfully established prokaryotic expression vector pET-28a/LF253,and sLF253 was expressed and purified. Western blot and ELISA results showed that sLF253 had an excellent antigenicity. Cellular toxicity detection showed that recombinant protein neutralized the biological effects caused by lethal toxin in vitro and in vivo. Conclusion:Recombinant sLF253 can recognize PA and competitively inhibit LF polymerization with PA to block its lethal effects. This protein may lay the experimental basis for the future of anthrax vaccine research and development.