Despite great progress, it is still one attractive topic to explore new controlled ring-opening polymerization method to fabricate well-defined polypeptides. Considering the activation of organophosphates and the polymerization characteristics of N-carboxyanhydrides (NCA), we herein describe an effective (S)-1,1'-binaphthylbased phosphoric acid catalytic system that mediates controlled ring-opening polymerization (ROP) of gamma-benzyl-L-glutamate N-carboxy-anhydrides (BLG-NCA) with primary amines as initiator. In the presence of (S)-2,2'-dimethoxyl-1,1'-binaphthyl phosphoric acid ((S)-1e), ROP with various feeding ratios of BLG-NCA to initiator afforded poly(gamma-benzyl-L-glutamate) (PBLG) with expected molecular weights (5.0-32.7 kg/mol) and relatively narrow dispersities (M-w/M-n = 1.05-1.16). The kinetics and chain extension experiments were conducted to identify that (S)-1e-catalyzed ROP of BLG-NCA in a controlled/living manner. A probable interaction between (S)-1e and the amine group of initiator/polymer chain-end was verified from H-1 NMR, P-31 NMR experiments. A plausible phosphate-ammonium mode catalyzing ROP of BLG-NCA was discussed.