A new type of molecular bottlebrush with poly-L-lysine (PLL) as backbone was synthesized via ROP followed by ATRP. A N?-bromoisobutyryl functionalized Na-CBZ-L-lysine was firstly synthesized and converted in polymerizable a-amino acid N-carboxyanhydride (NCA), which was then polymerized using Ni(0) transition metal complex to give well-defined bromo-functionalized homopolypeptide (PBrLL), from which we prepared two types of polypeptide bottlebrushes with polystyrene and poly(oligoethylene glycol methacrylate) as side-chains. PBrLL macroinitiator was demonstrated to have high initiation efficiency for ATRP, which allowed good control over side-chain length. CD and FTIR characterization revealed that both PBrLL macroinitiator and PLL backbone of bottlebrushes adopted a-helical conformation in appropriate solvents.