Porcine circovirus type 2 (PCV2) is an important causative agent of postweaning multisystemic syndrome in pigs,and both replicase proteins (Rep and Rep) encoded by PCV2-ORF1 are essential for the viral replication.To identify the antigenic epitopes,the monoclonal antibody (McAb) against the Rep protein of porcine circovirus type 2 (PCV2),BALBc mice were immunized with the purified recombinant PCV2-rRep protein expressed by baculovirus system.A cell line of hybridoma screening McAb to the Rep protein were prepared by means of lymphocyte hybridoma technique.The obtained McAb was named as 3D 1.The McAb isotypes was identified to be IgGl-kapa,and its antibody titer of ascites was 1:819 200.Western blot analysis showed that the McAb could react with both of the recombinant PCV2-rRep and PCV2-rRep proteins expressed by baculovirus.