Silver (Ag) nanowires with five-twinned structure were synthesized by chemical reduction method through the polyol process, in the presence of capping agents. The obtained silver nanowires are well-high monodispersed with the average diameter of 80 nm and length of 50 μm. Micro-scopical structures in these nanowires could be varied from nanoparticles and nanorods to nanowires by controlling the reaction conditions such as reaction temperature, molecular weight of PVP, kinds of seed materials, and changes of liquid polyols. Nanoparticles of platinum groups play roles of seed materials for the heterogeneous nucleation and growth of silver because of their close fitness in crystal structure and lattice constant. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD) and UV-visible spectroscopy were used to characterize silver nanowires.