The invention relates to a PCV3Cap protein epitope peptide, an anti-PCV3Cap protein monoclonal antibody, and a preparation method and application thereof. The invention provides the anti-PCV3Cap protein monoclonal antibody, and further provides a heavy chain variable region sequence and a light chain variable region nucleotide and amino acid sequence of the monoclonal antibody. On the basis, the antibody can be prepared by a genetic engineering method; and meanwhile, modification such as addition, deletion and replacement of one or more amino acids can be performed by genetic engineering and protein engineering methods to obtain an active fragment or a conservative variant thereof, thereby laying a foundation for further improving the specificity and affinity of the antibody. The antibody has relatively high specificity, has no cross reaction with PCV1, PCV2 and other porcine viruses such as CSFV, PRRSV and PRV, and has wide research and application values and commercial use values in immunological detection such as antigen/antibody detection kits, antigen/antibody immunochromatographic test paper, IFA, IPMA and Western Blotting.