Abstract: Provided are a protein antigen subjected to site-directed mutation and site-directed modification, and a method for site-directed mutation and site-directed modification of the protein antigen. The method comprises: site-directedly introducing an unnatural amino acid into a specific site of the protein antigen by genetic codon expansion technique; and performing site-directed modification with the protein antigen by the unnatural amino acid and a modifier, wherein the modifier is a receptor agonist such as tripalmitoyl-S-glyceryl cysteine and monophosphoryl lipid A. Further provided is use of the protein antigen subjected to site-directed mutation and site-directed modification, such as use as a vaccine.