The gIL-18 gene was cloned into pET32a(+) vector. The recombinant plasmid pET-gIL-18 in E.Coli BL21(DE3) was introduced by 1mmol/L IPTG for 4h or more time for expression. The fusion protein of pET and gIL-18 was expressed. SDS-PAGE analysis suggests that the recombinant protein is about 38ku. Western-blotting indicated recombinant gIL-18 showed well reaction to its specific multi-antibodies. The recombinant protein can stimulate the proliferation of PBMCs and induce IFN-γproduction in MDBK cells after denature、renature and purified. The recombinat protein also can protect mice against the attack of PRV virulent strains. Which are helpful for the clinical use of this cytokines.