IV core P27 gene was directly amplified from the monkey's PBMCinfected with SIVmac by method of PCR. The P27 gene was digestedwith EcoRI and SalI, and inserted into the EcoRI and Sall site of the exp-ression vector PBV220. The recombinant plasmid named PBVSG was vertifiedby DNA sequencing. When the expression plasmid PBVSG was transferred toE.coli DH5a and then induced at 40 , a product with the expected molec-ular weight ( 27KD ) was observed, which was approximately 14.5%of the total bacterial proteins. By Western blotting, the expressed proteinretained the reactivity with the SIV P27 monoclonal antibody and thespecific anti-SIV serum antibody in SAIDS model monkeys.