Self-assembling of synthesized novel biodegradable hyperbranched amphiphilic poly(ethylene glycol)-polyethylenimine-poly(epsilon-benzyloxycarbonyl-l-lysine) (PEG-PEI-PLys(Z)) in aqueous media is studied. In aqueous media, PLys(Z) is the hydrophobic segment, with PEG and PEI as the hydrophilic segments. It will self-assemble into spherical shape when the selected solvent water is dropped into the common solvent tetrahydrofuran (THF). And when PEG-PEI-PLYS in common solvent is dropped into mixed solvent water and THF, rings will come into being. The spherical and rings are observed by environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM). It shows that the size of the sphere is about 100 nm, and the diameter of ring distributes from 400 nm to 10 microm and bigger with the time roll around. It also forms a large vesicle with a thick edge by another method, which is good for drug delivery.