Abstract: Polypeptides are amino acid polymers. Due to their unique rigid chain structure and excellent biocompatibility, their self-assembled structures have the advantages of easy regulation, simple preparation, and rich morphology, which have attracted much attention in fields such as biomedicine and nanomaterials. In this paper, the polystyrene-block-poly(γ-benzyl-L-glutamate) (PS-b-PBLG) polypeptide-based block copolymers were obtained via anionic ring opening polymerization. Through transesterification reaction between the benzyl and polyethylene glycol, polystyrene-block-(poly(γ-benzyl-L-glutamate)-co-poly(ethylene glycol)-L-glutamate) (PS-b-P(BLG/PEGLG)) block graft copolymers were obtained. The self-assemblies were prepared by a selective precipitation method. PS-b-PBLG or PS-b-P(BLG/PEGLG) copolymers were first dissolved in THF-DMF mixture solvent. By adding water to the solution, core-shell particles were obtained, in which the hydrophobic PS segments formed the spherical core and the hydrophilic P(BLG/PEGLG) segments formed shell. The morphologies and structures of the formed aggregates were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atom force microscopy (AFM), ultraviolet-visible spectrophotometer (UV-Vis), and laser light scattering measurements (LLS). PS-b-PBLG copolymers form spherical micelles, and PS-b-P(BLG/PEGLG) copolymers form novel bowl-like nanostructures. The effects of length and degree of grafting, assembling temperature and rate of the water addition on the morphologies of the aggregates self-assembled from PS-b-P(BLG/PEGLG) were investigated. With increasing the degree of grafting and graft length, the hollows of bowl-like micelles increase, and eventually toroids are formed. The formation mechanism of nanobowls is proposed. With the induction of water into PS-b-P(BLG/PEGLG) copolymers solution in THF-DMF mixture solvent, primary micelles with a PS core and a P(BLG/PEGLG) shell are formed. As water content increases, the organic solvent within the primary self-assembled micelle core diffuses outward, while the core of the micelles remains impermeable to water. Consequently, the micelles collapse into nanobowls. For the PS-b-PBLG copolymers or the P(BLG/PEGLG) copolymers with low PEG graft ratio, the polypeptide segments in the shell are densely packed, resulting in a relatively rigid shell. During the outward diffusion of the organic solvent, the micellar morphology is less prone to deformation, and a spherical structure is maintained. When the PEG content is higher, the polypeptide segments in the shell exhibit greater mobility. As the organic solvent diffuses outward, the micelles display a larger hollow, and in some cases, even form nanotoroid structures.