Fe/Al2O3 and Fe3Al/Al2O3 composites were prepared by mechanochemical synthesis. Microwave characteristics were measured in 0.1–18 GHz. A reflection loss (RL) exceeding -10 dB in the frequency range of 1.5-8.5 GHz for an absorber of 6-1.5 mm was achieved for the Fe3Al/Al2O3 composites. Optimal RL of -41 dB was obtained at 2.8 GHz for an absorber thickness of 3.9 mm. The good microwave-absorption properties results from a proper impedance match as a consequence of the insulator Al2O3 around Fe and Fe3Al. Microwave reflection results show that the corresponding frequency and the matching thickness is closely related to the quarter wavelength matching condition and these composites can be attractive candidates for electromagnetic wave absorption materials.