Abstract: Iron minerals' phase transformation and magnetic properties' variation were investigated with magnetic detection, X-ray diffraction and Mössbauer spectra on JISC's refractory powder ferrous material (-0.30 mm) which was rich in specularite, limonite and Mg-Mn siderite. The results of XRD analysis and Mössbauer spectra records of the iron material before and after FMR indicate that weakly magnetic iron minerals is mainly converted into strongly magnetic material Fe₃O₄ with many cracks in iron material after FMR. The efficiency of FMR are consistent with TFe recovery of magnetic separation, meantime, the specific saturation magnetic moment increase from 33 to 42 times after FMR. In the process of FMR, magnetization transformation of Mg-Mn siderite is mainly controlled by chemical reaction, but that of specularite by diffusion and part of it not magnetized.