When the spike protein of SARS-CoV-2 binds to the receptor of the host cell, the virus enters the cell, and then the envelope is peeled off, which let genomic RNA be present in the cytoplasm. The ORF1a and ORF1b RNAs are made by genomic RNA, and then translated into pp1a and pp1ab proteins, respectively. Protein pp1a and ppa1b are cleaved by protease to make a total of 16 nonstructural proteins. Some nonstructural proteins form a replication/transcription complex (RNA-dependent RNA polymerase, RdRp), which use the (+) strand genomic RNA as a template. The (+) strand genomic RNA produced through the replication process becomes the genome of the new virus particle. Subgenomic RNAs produced through the transcription are translated into structural proteins (S: spike protein, E: envelope protein, M: membrane protein, and N: nucleocapsid protein) which form a viral particle. Spike, envelope and membrane proteins enter the endoplasmic reticulum, and the nucleocapsid protein is combined with the (+) strand genomic RNA to become a nucleoprotein complex. They merge into the complete virus particle in the endoplasmic reticulum-Golgi apparatus compartment, and are excreted to extracellular region through the Golgi apparatus and the vesicle.