The invention relates to a PCV2 (porcine circovirus 2) ELISA (enzyme-linked immuno sorbent assay) antigen detection kit as well as a preparation method and applications thereof, wherein the detection kit comprises an elisa plate of a polyclonal antibody of peridium anti-PCV2-Cap (nucleocapsid) protein, seal liquids, sample diluent, an antigen standard product, a second antibody of a monoclonal antibody of HRP marked anti-PCV2-Cap protein, a concentrated washing liquid, an enzyme substrate solution A, an enzyme substrate solution B and a stop solution, wherein the antigen standard product is purified reconstructed PCV2-Cap protein. The specificity of the kit provided by the invention achieves 100%, and the sensitivity is as high as 4ng/ml, and the kit can be used for swinery PCV2 antigen detection and PCV2 vaccine product quantitative detection.