Mono-dispersed silver nanoparticles with various morphologies were synthesized in large quantities by reducing silver nitrate with ethylene glycol in the presence of poly(vinylpyrrolidone) (PVP). The effects of the concentration of AgNO3, temperature, adding rates of PVP and AgNO3 injected into ethylene glycol as well as molar ratio between the repeating unit of PVP and AgNO3 were discussed. By varying the temperature and reaction time, silver nanocubes, nnoprisms and nanospheres were obtained. It is indicated that at elevated temperatures, the ethylene glycol can reduce Ag+ ion into Ag atoms, and thereby inducing the nucleation and growth of silver nanostructures in the solution phase. In the polymer-mediated polyol process, PVP plays a critical role in producing silver nanostructures with good stability and size/shape uniformity. As a result, both the crystallinity of a seed and extent of PVP coverage on the seed were instrumental in controlling the morphology of Ag nanoparticles.