Monodisperse silicon dioxide particles have been prepared by the seed growth method

and different coupling agents were used for modifying these silica particles．The results show that the size deviation of silica particles modified with[3-(methacryloyloxy)pmpyl] trimethoxysilane(KH-570) is much lower than that of silica particles modified with vinyl triethyloxy silane as the coupling agent．In the presence of ethanol and water

styrene may react with silica modified by KH-570 in dispersion polymerization．It was discovered through transmission electron microscopy and energy spectrum that the modified silica particles were successfully encapsulated with polystyrene．The number of silica particles encapsulated with polystyrene was continually decreased with the increase of the size of silica particles．Moreover

the number of silica particles was nearly unity in each SiO2/PS composite particle when the silica particle size was greater than 410 nm．