Based on the thermodynamics and kinetics theory, a theoretical model was built to illuminate the formation of metal nanopowders by anodic arc discharging plasma method, and the mechanism of particle nucleation and growth was investigated. In addition, the morphology, crystal structure, particle size and specific surface area of the nanopowders were characterized by X-ray diffraction(XRD), Brunauer-Emmett-Teller(BET) adsorption, transmission electron microscopy(TEM) and the corresponding selected area electron diffraction(SAED). The experimental results indicate that the nanopowders prepared by this process have uniform size,high purity, single phase and spherical shape. The crystal structure is FCC structure, the same as that of the bulk materials; the specific surface area is 12 m2/g, the particle size distribution ranges from 30 to 90 nm with an average particle size of 67 nm which is obtained from TEM and confirmed from XRD and BET results.