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SiO2/Ag composite material was synthesized with polyvinylpyrrolidone (PVP) as both the reductant and stabilizing agent. The particle size and quantity of silver nanoparticles on silica spheres could be changed with [Ag(NH3)2]+ ions of different concentrations. Transmission electron microscope (TEM) and scanning electron microscope (SEM) analysis were used to characterize the SiO2/Ag composite material. Results show that the silver is deposited on silica spheres as polycrystalline nanoparticles. Raman spectrometer measurement shows that surface enhanced Raman scattering (SERS) performance is improved by increasing the quantity of silver deposition on silica.