The choleystokinin-33(cck-33) gene was synthesized based on the chicken(cck-33) sequence and E.coli codon bias.The cck-33 gene was inserted into plasmids pRSET A and its concatemer was constructed based on the fact that isocaudarner enzyme existed.The recombinant CCK protein was expressed in E.coli BL 21 and purified successfully.The purified protein was used as an antigen to prepare oil-emulsion vaccines and then to immunize Huxu chicken.The result indicated that the anti-serum P/N of chicken immunized with purified protein was higher than 2.