Nano-crystalline SmN/α-Fe and SmO/α-Fe double phase composite with electromagnetic (EM) wave absorption property was prepared by hydrogenization and dehydrogenization followed by nitrogenation and oxidation treatment. The results show that the measured real part and imaginary part of dielectric constant for SmN/α-Fe are higher than that for SmO/α-Fe, but the complex EM permeability of SmO/α-Fe is higher than that of SmN/α-Fe, their imaginary parts of the relative permeability μ″ exhibit two resonant peaks and high values over the 0.5~18 GHz range. Because the match between the permeability and the dielectric constant for SmO/α-Fe is better than that for SmN/α-Fe, therefore the former has better EM wave absorption property and its RL (reflection loss) is less than –20 dB with absorber match thickness of 1.60~3.95 mm in the frequency range of 3.30~10.65 GHz. The minimum RL is –50 dB, absorber match thickness is 2.92 mm at 4.8 GHz.