Abstract: Disclosed are a SARS-COV-2 antigen polypeptide, a recombinant adeno-associated virus (rAAV) expressing the polypeptide, and a vaccine containing the virus. A sequence of the antigen polypeptide is shown in SEQ NO. 1. and SEQ ID NO. 2. A method for preparing the recombinant adeno-associated virus comprises co-incubating pHelper, pRep2Cap5, and an expression vector, transfecting a cell in the presence of polyethyleneimine as a transfection reagent; culturing the cell, then collecting the cell by centrifugation, performing lysis and purification to obtain a purified liquid comprising the recombinant adeno-associated virus. The rAAV is delivered and expressed in vivo to produce a fusion antigen polypeptide, induces the production of serum neutralizing antibodies, which have a neutralizing titer to the novel SARS-COV-2 coronavirus and are expressed continuously; the rAAV composition can be used to immunize humans against the novel coronavirus pneumonia COVID-19.