A kind of novel triblock copolymers of poly(y:benzyl L-glutamate)-b-poly(tetrahydrofuran)-b-poly(γ-benzyl L-glutamate)s (PBLG-b-PTHF-b-PBLG) was synthesized by using bis(3-aminopropyl) terminated polytetrahydrofuran to initiate the ring-opening polymerization of γ-benzyl L-glutamate N-carboxyanhydride (BLG-NCA). The corresponding multiblock poly(amino aeid-urea)s were prepared in one-pot protocol from the chain extension of PBLG-b-PTHF-b-PBLG with MDI. The resulting triblock and multiblock copolymers were characterized by FFIR, 1H-NMR, 13C-NMR and GPC techniques. It is demonstrated that the chain extension has taken place to give rise to the copolymers with the well-defined block composition and narrow molecular weight distribution. A distinct Tg arising from the hard-segments was observed in all the copolymers. Their mechanical properties showed an increasing trend with the molecular weight enhancement of the prepolymers.