Nanometer silver sol was synthesized via γ-rays liquid irradiation reduction with polyvinyl alcohol as the protective agent, and morphology, size and aggregation state of nano-silver particles were also characterized by TEM, HRTEM, and XRD. Moreover, the relationship between the morphology, size and dispersion and reaction conditions was also investigated and discussed. The result shows that lower absorbed dose and silver nitrate concentration (0.01 mol/L), higher polyvinyl alcohol concentration (7.5%), and suitable isopropanol concentration (0.5 mol/L) prefer to form the smaller size (10−30 nm), monodisperse and good dispersion nano-silver sol, which has been found to be the face-centered cubic single crystal. It could describe the growth mechanism of nanosilver forming process as three steps, crystal nucleation after the silver cation is reduced to Ag, the nucleus growing and forming primary particles, and the second particles form after aggregation of the primary particles.