|The spike (S) glycoprotein of coronaviruses contains protrusions that will only bind to specific receptors on the host cell. The spike is essential for both host specificity and viral infectivity. The spike (S) glycoprotein of coronaviruses is known to be necessary for the binding of the virus to the host cell at the advent of the infection process. It has been reported that SARS-CoV-2 can infect the human respiratory epithelial cells through interaction with the human ACE2 receptor. The spike protein is a large type I transmembrane protein containing two subunits, S1 and S2. S1 mainly contains a receptor-binding domain (RBD), which is responsible for recognizing the cell surface receptor. S2 provides essential elements needed for membrane fusion. The S protein plays vital parts in the induction of neutralizing-antibody and T-cell responses, as well as protective immunity. The main functions for the Spike protein are summarized as Mediate receptor binding and membrane fusion; Defines the range of the hosts and specificity of the virus; the Main component to bind with the neutralizing antibody; Key target for vaccine design; Can be transmitted between different hosts through gene recombination or mutation of the receptor-binding domain (RBD), leading to a higher mortality rate.