Abstract: To optimize the secretory expression efficiency of the BVDV（Bovine Viral Diarrhea Virus） E2 protein in eukaryotic cells， eight recombinant expression plasmids carrying different signal peptides were constructed and transiently transfected into 293T cells. E2 protein expression was detected by Western blot， and its secretory expression efficiency was evaluated by comparing E2 protein levels in the cell culture supernatant and cell lysate， through which the optimal signal peptide was screened. Based on the screening results， the expression was scaled up and the protein was concentrated， and the biological activity of the expressed E2 protein was assessed by examining its protective effect on MDBK cells against BVDV infection. The results showed that the recombinant plasmid containing the Influenza Hemagglutinin signal peptide achieved the highest secretory expression efficiency of E2 protein. The secreted E2 protein was able to protect MDBK cells from BVDV infection in a concentration‑dependent manner， indicating that the obtained E2 protein possessed favorable biological activity. An experimental and theoretical basis were provided for optimizing the eukaryotic secretory expression system of the BVDV E2 protein， as well as for further investigation of its function and the development of subunit vaccines.