When the fraction of inordinate component on the interface or/and surface in nanostructured FeAl is comparable to that of crystal grain which is wrapped up in the former,and there exists Fe-Al-Fe surperexchange or/and Fe-Fe exchange interactions in the inordinate component on the interface or/and surface, a nonmagnetism—magnetism transition between polycrystall FeAl alloy and nanostructured FeAl would result.There was no signal of magnetic resonance in the bulk polycrystal FeAl from the experimental results of electron spin resonance (ESR) in X wave band with a frequancy of 9.48GHz.The ferromagnetic resonance (FMR) signals were observed in the nanostructured samples, whose line widths ΔHpp were over 8×104A/m.Otherwise,an ESR fine structural signal of double peaks of Fe2+ ion was also observed in nanocrystal line samples, the interval of the two peaks was 1.316×105A/m,and the ΔHpp of each peak was smaller than 800A/m.The configuration of the paramagnetic Fe2+ was 3d54s1, and spin quantum number was S＝1,its zero-field splitting D was 2.448GHz,or 10.12×10-6eV.An overlap of the ESR double peaks of paramagnetic Fe2+ and the wide FMR peak resulted in two sharp peaks like resonant singularities on the FMR spectrum.