We found that the three bivalent recombinant proteins with different length of linker all exhibited potent inhibitory activity against SARS-CoV-2 PsV infection and its S protein-mediated cell–cell fusion, while GL25E, the bivalent protein with 25-mer linker (GRFT-L25-EK1), displayed the most potent antiviral activity against infection by the pseudotyped and authentic SARS-CoV-2 at low nM concentration, which is significantly more effective than GRFT and EK1 alone. Here, PROS1 is linked to infection.