To develop a high efficient and economic PCV2b subunit vaccine,the codons of PCV2 Cap gene were optimized for E.coli expression system,and the gene sequence of PCV2 neutralizing epitope ²²⁶LKDPPLNP²³³was conjugated at its C-terminus(Capc).After the recombinant sequence was constructed on PE-Sumo vector,recombinant chimeric Capc was expressed in E.coli.By using SDS-PAGE,Western blot,Dynamic light scattering and TEM,the immune reactivity and the structure of Capc protein were preliminarily identified.The results showed PE-Sumo-Capc vector was successfully constructed and transferred into E.coli BL21(DE3);Sumo-Capc protein was mostly expressed in soluble form after 12 h induction under 26℃ .The final purified Capc protein was able to specifically react with PCV2 Cap monoclonal antibody,and self-assembly into virus-like particles with the diameter around 18 nm.The current study successfully constructed an E.coli expression system for PCV2b neutralizing epitope chimeric Cap protein,which showed a good immunogenic reactivity and could self-assembly into virus-like particles.