The invention discloses a detection method of a new coronavirus SARS-CoV-2 antigen, and belongs to the technical field of biology. The method comprises the following steps of capturing nanoparticles by virtue of new coronavirus SARS-CoV-2S protein immunomagnetic beads, carrying out specific immunization on the nanoparticles and S protein, and incubating with immune gold signal nanoparticles so as to construct a sandwich structure; detecting an SERS signal through a Raman spectrometer, specifically detecting the new coronavirus SARS-CoV-2 protein within 5 minutes, and specifically detecting the pseudovirus and variant pseudovirus of the SARS-CoV-2 and the pseudovirus diluted in human saliva. Through the above mode, nucleic acid extraction or antibody-dependent detection is not needed, meanwhile, the method has the advantages of being good in stability, higher in specificity and affinity, low in immunogenicity, easy to chemically modify, simple and convenient to operate and the like, the rapid detection of the new coronavirus SARS-CoV-2 antigen and the variant virus can be achieved within five minutes, and a condition is created for the early detection of the 2019SARS-CoV-2 pathogen.