The biological protein synthesis system has been engineered to incorporate unnatural amino acid into proteins, and this has opened up new routes for engineering proteins with novel compositions. The novel compositions allow that proteins are modified site-specifically by bio-orthogonal method. While such systems have been successfully applied in research, there remains a need to develop new approaches with respect to the wider application of unnatural amino acids. In this study, we reported a strategy for incorporating unnatural amino acids into proteins by reassigning one of the Arg sense codons, the AGG codon and four-base codon, AGGA codon. Using this method, several unnatural amino acids were quantitatively incorporated into the AGG and AGGA sites. And we applied the method to multiple AGG and AGGA sites, and even to tandem AGG and AGGA sequences. The method developed and described here could be used for engineering proteins with diverse unnatural amino acids, particularly when employed in combination with other methods. Moreover, monoclonal cell-penetrating antibody, cytotransmab was conjugated to biomacromolecule site-specifically using unnatural amino acid and it was demonstrated that the cytotransmab conjugate deliver the biomacromolecule into the cytosol.