Monodisperse polystyrene(PS) microspheres with average sizes of 1.2 to 1.5 μm were obtained by emulsion polymerization. Using PS microspheres as the cores, some PS/Ag core shell particles were prepared after ultrasonic sensitization, deoxidization and electroless process. Their morphology, component, structure and optical properties were characterized and investigated by transmission electron microscopy, X-ray diffraction, infrared ray, and UV-Vis adsorption spectra. The results indicate that the size distribution of the composite particles is narrow and the shell thickness of silver can be controlled by multiple sensitization and adjusting the second concentration of [Ag(NH4)2]+, from 0.002 to 0.006 mol/L. In addition, while the silver nanoparticles coated on the polystyrene grows, the