In this paper, we proposed a facile method to obtain the lightweight composites consisting of surface modified Fe50Ni50-coated poly(acrylonitrile) microspheres (PANS@SMF), reduced graphene oxide (RGO) and epoxy resin. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM) and vector network analyzer (VNA). Impedance matching condition and electromagnetic wave attenuation characteristic were used for the reflection loss (RL) performance of the composites. Compared with pure PANS@SMF and RGO composites, the −10dB absorption bandwidth and the minimum RL of the hybrid composites were enhanced. The bandwidth less than −10dB was almost 4.5GHz in the range of 10GHz to 14.5GHz, with a matching thickness of 2.5mm. The density of the hybrid composites was in the range of 0.25–0.34g/cm3. Therefore, the hybrid composite can be considered as a potential lightweight microwave absorber.