In this study, a series of functional peptide-based RAFT agents were designed and synthesized by the solid-phase supported peptide synthesis method. These novel RAFT agents have enabled chemists to make well-defined peptide-polymer conjugates with complicated topological structures. Additionally, our results have shown an unexpected reaction that takes place during these syntheses, and the conversion of a nitrile group to a carboxamide group has been evidently elucidated and unambiguously confirmed.