Abstract: High-stable and monodisperse colloidal nano-silver particles were synthesized by reduction of ［Ag(NH3)2］+ with hydrazine hydrate using sodium citrate as stabilizer and polyvinylpyrrolidone(PVP) as dispersant. Furthermore, nano-silver/polystyrene composite was prepared via microemulsion polymerization.The optical properties of the nano-silver particles were studied by ultraviolet-visible (UV-Vis) absorption spectra, and the crystal structure and microscopic morphology were characterized via X-ray diffraction(XRD) and transmission electron microscopy(TEM), respectively. Results show that, the nano-silver particles belong to cubic crystal system and have an average diameter of 10 nm without aggregation and oxidation, and their crystal structure and microscopic morphology do not change obviously during the process of polymerization. Gel permeation chromatography(GPC) data shows that the weight-average molecular weight of polystyrene matrix is over 4.03106, and the molecular weight distribution index is 1.21. Thermal gravity-differential scanning calorimetry(TG-DSC) test demonstrates that the nano-silver/polystyrene composite has excellent thermal stability.