In this research, we provide a facile method to development of band width electromagnetic absorber via loading magnetic quantum dots on the mono-dispersed amorphous carbon sphere. The phenolic resin sphere (RS)/Feglycolate has been successfully prepared firstly through thermal-decomposition method. By another high-temperature carbonatization process, the phenolic resin sphere, Fe-glycolate were converted into amorphous sphere and Fe3O4 or Fe quantum dots, respectively. The dielectric loss and electromagnetic absorption properties becomes stronger at elevated carbonatization temperature. This is can be explained that carbon sphere at high temperature can gradual reduce the Fe3O4 quantum dots to Fe, leading to the boosted polarization and conductive loss ability. Besides, the reduction degree is controllable by adjusting the carbonatization carbon sphere/ Fe-Fe3O4 obtained at 700 degrees C shows excellent electromagnetic absorption properties which the effective electromagnetic absorption region covers 5.8 GHz with a coating thickness of 1.5 mm. To better understand of the absorption mechanism, the contributions of carbon sphere, Fe, Fe3O4 have been discussed in depth.