The core-nanoshell composite materials doped with Sm were prepared by a solid-state reaction method. The core is magnetic fly-ash hollow cenosphere, and the shell is the nanosized ferrite doped with Sm. The thermal decomposition process of the sample was investigated by thermogravimetric analysis-differential scanning calorimetry ( TG- DSC ). The morphology and composition of the composite materials were investigated by the X-ray diffraction analysis ( XRD ), scanning electron microscope ( SEM ) and energy disperse spectroscopy ( EDS ). The results of vibrating sample magnetometer analysis ( VSM ) indicated that the exchange-coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which caused outstanding magnetic properties. The results show that doped with Sm can enhance the coercivity too, so the magnetic properties could be promoted further by the adjustment of compositions and the use of special techniques. The magnetic properties of the core-nanoshell composite material are better than that of single-phase.