This article reports the facile synthesis of monodisperse polymer hollow spheres by seeded emulsion polymerization without additional treatment. In this method, P(St-MMA-MAA) copolymer latex particles were first prepared by emulsifier-free emulsion polymerization and then used as seeds to carry out emulsion polymerization of methyl methacrylate (MMA), divinyl benzene (DVB), and 2-hydroxyethyl methacrylate (HEMA) with potassium persulfate (KPS) as initiator at 80 degrees C. The void of hollow spheres was readily adjusted by changing the monomer/seed weight ratio, and it could be enlarged while the diameters of hollow spheres changed little after etching by dimethyl formamide (DMF). The effects of synthetic parameters including the monomer composition and the properties of seeds on the morphology of hollow spheres were investigated in detail. On the basis of the experimental results, it seemed reasonable to conclude that the formation of hollow spheres was due to the "dissolution" of seeds in monomers and phase separation between the constituent polymers. As a thermodynamic factor, sodium dodecyl sulfate (SDS) would allow the preparation of solid particles depending on its level.