(Arg)9 peptide is a cell-permeable peptide consisting of 9 consecutive arginines. (Arg)9 has a very efficient internalization effect, can effectively enhance the protein's membrane transfer function, and can greatly improve the internalization efficiency when used as a primer. In peptide synthesis, the continuous coupling of 9 arginines is difficult, but under different condensing agents and solvent systems, continuous coupling of more arginines can be achieved.