Poly(ethylene glycol)-block-poly(γ-benzyl L-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer and poly(γ-benzyl L-glutamate)-graft-poly(ethylene glycol) (PBLG-graft-PEG) copolymer were synthesized by the ester exchange reaction of PEG chain with PBLG-block-PEG copolymer and PBLG homopolymer, respectively. The micellization behaviors of PEG-b-PBLG-g-PEG and PBLG-graft-PEG in ethanol were investigated by transmission electron microscopy (TEM) and viscometry. Effects of both the introduction of PBLG homopolymer and the change of testing temperature on the critical aggregation concentration (CAC) of the two polypeptide copolymers in ethanol were mainly studied. Nuclear magnetic resonance (NMR) spectroscopy and fourier transform infrared spectroscopy (FTIR) were used to research the chain conformations of polypeptide segments of the two polypeptide copolymers in solvent and in the solid state, respectively.