A flaky Fe-based mangetorheological elastomer film (F-Fe/MREF) composite was developed through mixing micron-sized flaky Fe particles into a silicone rubber (SR) matrix by compression molding and vulcanization. The 28 wt % F-Fe/MREF with a thickness of 4.3 mm displays dual resonance peaks with an optimal reflection loss (RL) value of -53.3 dB at 4.8 GHz and an effective frequency bandwidth (RL < -10 dB) reaches 6.0 GHz. Furthermore, anisotropic F-Fe/MREF obtained by assistance of an external magnetic field demonstrates an effective bandwidth of 12.5 GHz in one thickness. This is attributed to the synergistic contributions from magnetic loss and dielectric loss and good impedance matching along with promotion of multiple reflections and scatterings. Besides, an MR effect of 39.2% was obtained for anisotropy F-Fe/MREF because of interaction enhancement between F-Fe particles and the cross-linked matrix. These results suggest that the F-Fe/MREF composites could serve as a potential candidate toward applications of electromagnetic wave absorbing.