Monodispersed SiO2/Ag core-shell nanoparticles have been synthesized successfully via a facile and fast route. Morphology of the product was investigated by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) technique. It has been revealed that the diameter of SiO2/Ag compostie was ca. 220 nm and the shell of Ag nanoparticle are homogeneous and monodispersed. The antibacterial activities of SiO2/Ag core-shell nanoparticles were tested by means of minimal inhibitory concentration (MIC) and viable cell counting method. The results showed that the SiO2/Ag presents a good antibacterial performance against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans), which indicated its potential applications as antibacterial material for microbiocides.