Abstract: Micron-size polystyrene(PS)/polysiloxane microspheres with core/shell structure were synthesized.Firstly, polystyrene microspheres were prepared by conventional dispersion polymerization in an ethanol-water medium. Secondly, methyl trimethoxylsilane was hydrolyzed, mixed with the polystyrene core microspheres and then condensed to generate polysiloxane shells in the surface of PS microspheres by adding an aqueous NH₄OH as catalyst. The shape, size distribution, surface composition and thermo decomposition of core/shell microspheres were investigated with TEM, size analyzer, EDX and TG respectively. This core/shell microspheres as light scattering agents were blended with polymethyl methacylate（PMMA） resin to prepare light scattering material. When the concentration of core/shell microspheres SS6 was 1%(mass), the haze of PMMA sheet（2mm） was 88.16%,transmittance was 72.5%. When the concentration of SS6 was 2%(mass), the haze of PMMA sheet was 92.13%.