Display omitted •Fe3O4@LAS/RGO composites with uniform size were successfully synthesized.•Fe3O4@LAS/RGO composites have excellent microwave absorption performance and broad bandwidth.•The addition of lithium aluminum silicate glass-ceramic contributes to the synergy of dielectric loss and magnetic loss.•A multiple transmission-absorption mechanism was introduced for the material to effectively improve impedance matching. For the first time, Fe3O4@LAS/RGO composites with uniform size and extraordinary electromagnetic wave absorption properties were successfully synthesized by a simple three-step method. The Fe3O4 nanospheres with a diameter of about 200 nm are tightly attached by the lithium aluminum silicate (LAS) glass-ceramic particles with a diameter of about 20 nm and evenly distributed among the graphene sheets. The method of coating a microwave absorber with a wave-transparent material introduces a multiple transmission-absorption mechanism for the material to effectively improve impedance matching. The input impedance Zin value (∼1.0) of Fe3O4@LAS/RGO is better and more stable than the Zin value (∼1.2) of Fe3O4/RGO. The RL values of Fe3O4@LAS/RGO could reach −65 dB at 12.4 GHz with a thickness of only 2.1 mm and the absorption bandwidth with RL values less than −10 dB (over 90% electromagnetic wave absorption) is up to 4 GHz at the corresponding thickness. The intrinsic properties of the component of Fe3O4@LAS/RGO composites and the composite structure of the material lead to a variety of microwave absorption mechanisms acting together to improve the microwave absorption properties of the composites.