Spherical silica particles doped with silver nanoparticles were prepared in a water/oil emulsion by the sol-gel reaction of TEOS. Aqueous silver colloid solution as water phase and n-decyl alcohol as the oil phase were used in emulsion. Span 80 was used to form the W/O emulsion. The stability of the emulsion during the sol-gel reaction was a crucial factor for the formation of spherical silica particles. Without the oil-soluble polymer in the decyl alcohol as an emulsion stabilizer, the spherical silica particles were not formed. Also the high viscosity of the aqueous droplets caused by adding the water-soluble polymer in the silver colloid solution hindered the formation of spherical silica particles. This might be due to the limited movement of hydrolyzed TFOS molecules in the aqueous droplets. The amount of silver nanoparticles in the colloid solution did not influence the shape of the particles. The size of the spherical silica particles was 1-3 mum and the silica particles were composed of 83.6 atomic % of Si and 16.4 atomic % of silver.