Poly(-benzyl L-glutamate)-block-poly(ethylene glycol) (PBLG-block-PEG, PEG as random coil polymer) was synthesized by a standard N-carboxyl--benzyl-L-glutamate anhydride method. The surface morphology of PBLG-block-PEG copolymer aggregates from the dilute solution was studied by scanning electron microscopy (SEM). The effects of precipitation temperature, precipitation time, various solvent systems, and copolymer solution concentration on the surface morphologies of the polypeptide block copolymer aggregates from the dilute solution were investigated.