Abstract: CeO₂/SiO₂ composite nanoparticles with complete core-shell structure were prepared through homogeneous precipitation method using commercial silica sol as silicon resource. The phase composition and nanotopography of the as-prepared particles were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The effect of pH value on the dispersity of CeO₂/SiO₂ composite nanoparticles in water suspension was studied by the analysis of size distribution and Zeta potential. The results indicated that the as-prepared composite nanoparticles possessed a complete core-shell structure which composed by amorphous silica core and cubic fluorite ceria shell. The particle size was about 110 nm. The equipotential point of CeO₂/SiO₂ composite nanoparticles was about pH5, and its value was significantly shifted from the equipotential point of SiO₂ to the equipotential point of CeO₂. The as-prepared composite nanoparticles agglomerated easily under the acidic condition, while dispersed well under the alkaline condition.