Abstract: we firstly adopted the method of concentration of the virus and extract its genome. Than referring to the sequence which is published in Gene Bank, we designed a pair of primers. product of the PCR amplification , pIX protein ,was analyzed by agarose gel electrophoresis and demonstrated to be a specific band of 1099bp.The fragment was cloned into the pMD18-T vector. After cloning it into the T vector, we sequenced the targeted fragment and the result showed that it was right. Then we ligated it into the expression vector pGEX-4T-1 with DNA T4 ligase, which is digested by the same two enzymes. Furtherly digesting by EcoRI and SalI for identification, we finally got the positive expression vector pGEX-4T1-IX. After transforming the recombinant plasmid pGEX-4T1-IX to the host E.coli BL21(DE3)for 2~3 hours ,we induced it by IPTG with the terminal concentration of 1mmol/L.The whole quantity of expression is up to 21% in the host cell. In the Western Blotting assay , the protein expressed can be detected by CAV-I positive serum, which will contribute greatly to the establishment of CAV-I antibody detecting method.