Nanowire arrays of the alloy, Fe0.68Ni0.32, with different nanowire diameters have been fabricated by the electrochemical deposition method.X-ray diffraction and M.ossbauer spectroscopy were employed to characterize the size effect on the structure and micro-magnetic properties of the nanowire array, respectively.The Fe0.68Ni0.32 arrays with different diameters are stabilized in a BCC structure with a [110] texture oriented along the long axis of the nanowires.The M.ossbauer spectra of the nanowire arrays with smaller diameters show an absence of the second and fifth peaks, which then emerge with increasing diameter.The size effects on the hyperfine parameters are discussed.