Abstract: With 2,2′-azobis［2-methylpropionamidine］ dihydrochloride (AIBA) as the initiator, styrene(St), butyl acrylate (BA), quaternary ammonium cationic comonomers methacryloxyethyl trimethyl ammonium chloride (DMC) and trimethyl(vinylbenzyl) ammonium chloride (VBT) as the monomers, the emulsifier-free emulsion polymerization was carried out under thermostatic water bath 80 ℃ and 300 r/min stirring, and the ternary copolymer nanospheres of P(St-BA-DMC) and P(St-BA-VBT) were finally prepared. The effect of quaternary ammonium cationic monomers(DMC/VBT) on the structure and property of nanospheres was analyzed by transmission electron microscope (TEM), laser particle size analyzer, differential scanning calorimetry (DSC) test. Results indicated that the particle size of P(St-BA-DMC) first decreases then increases with increasing DMC amount, while the particle size of P(St-BA-VBT) decreases gradually with increasing VBT amount; Surface charge density and glass transition temperature increases with increasing amount of cationic monomer, respectively. What’s more, in the both different systems, there were two kinds of nanospheres with light and dark shadows seen from TEM. The reason may be that the more hydrophobic oligomer radicals formed in the nucleation process, the more nanospheres containing more PS-oligmers with higher density dominated in the system, otherwise, the less hydrophobic oligomer radicals, the more nanospheres containing more PBA oligmers with lower density were in majority in the system.