Silica nanoparticles for polymeric dental restorative composites were prepared by Stober method, and then the effects of surface treatment of silica particles with Lmethacrylofpropyltrimethofsilane $(gamma-MPS)$ on the dispersity of the silica particles in the organic matrix was investigated. Particles having various average size were prepared by using controlled amounts of tetraethylorthosilicate(TEOS), water, and catalyst and by changing solvent used for reaction. The site of particles prepared by using methanol as solvent was smaller than that prepared by using ethanol as solvent. In addition, the size of particles was increased by decreasing amounts of water and by increasing amounts of TEOS and catalyst. Hydrophobic silica nanoparticles was prepared by reacting hydrophilic nanoparticles with $gamma-MPS$ to improve interfacial properties with organic matrix. Amounts of $gamma-MPS$ per unit mass of the particles was increased by decreasing particle size. even though the amount of $gamma-MPS$ per specific surface area were nearly the same regardless of the particle size. The dispersity of the silica particles in the organic matrix was improved when the surface treated silica particles were used for preparing the polymeric dental restorative composites.