Abstract: To improve the electromagnetic wave absorption performance of graphene, the electromagnetic properties of RGO@Fe₃O₄ nanoparticle composites have been researched. RGO@Fe₃O₄ composites was prepared in a solvothermal system by reduction reaction between FeCl₃·6 H₂O and ethylene glycol in the presence of GO. SEM and XRD were used to characterize the structure of the composite and the distribution of Fe₃O₄. Vector network analyzer was used to measure the complex permittivity and complex permeability of the composite in the frequence range of 0.5~18 GHz. By the transmission line theory, the reflection loss was calculated. The results showed that the electromagnetic wave absorption performance of RGO@Fe₃O₄ composites was much better than that of Fe₃O₄; that with the increase of addition of FeCl₃·6 H₂O, the effective absorption bandwidth was broadened, and the maximal bandwidth could reach 1.8 GHz; that by changing the content of FeCl₃·6 H₂O and the thickness of material, minimum reflection loss could be as low as-44.2 dB.