Abstract: The phage display peptide library is a widely-used epitope identification technology,which is combined with the protein screening. Phage display technique was used to screen out the proteins interacted with ORF1B copy enzyme protein of porcine respiratory and reproductive syndrome virus （PRRSV） . And the antiviral activity of the screening protein was further verified. The purified CTD protein of PRRSV ORF1B that coated high-affinity 96T board was used as the target protein. T7 phage display technology was applied to screen out the cDNA library of random 12-peptide library. And the screened clones were sequenced and analyzed. After the synthesis of the screened clone sequence, the anti-PRRSV effect of the synthetic polypeptide was verified in vitro. The results showed that 87 positive clones were obtained after 4 circles of phage screening. 11 screened 12-peptide were identified after sequencing. Through in vitro antiviral experiment, it was confirmed that P10 was a 12-peptide with high-antiviral activity. These results laid the foundation for the antiviral research of PRRSV.