Disclosed is a SARS-CoV-2 vaccine, wherein the S protein of SARS-CoV-2 serves as the antigen, and the vaccine comprises an adenoviral vector, and the vaccine induces an improved protective immune response through mucosal immunity, thus preventing SARS-CoV-2 infection. Specifically, when atomized by an appropriate apparatus, the vaccine generates particles of improved uniformity, which can reach the lungs after being inhaled via the nasal cavity or the oral cavity, thus producing a protective immune response with respect to the entire respiratory tract and the lungs, enhancing the effective utilization rate of the vaccine, and increasing the effect of the vaccine.