Abstract: Developing lightweight and flexible thin films for electromagnetic interference (EMI) shielding is of great significance. In this paper, RGO@SiC porous thin films for EMI shielding were prepared by chemical reduction of mixtures of graphite oxide (GO) and SiC whiskers with HI, followed by microwave irradiation for 3 s. A significant increase of the film thickness from around 20 to 200 μm and further reduction of GO were achieved due to formation of a porous structure via expansion of interlayer space of GO with gases released by heating in 3 s of solid phase microwave irradiation. The total shielding effectiveness (SE_T) and the reflective SE (SE_R) of the RGO@SiC porous thin films were altered by the GO/SiC mass ratio, which reached the highest SE_T of 35.6 dB while the SE_R was only 2.8 dB when the ratio was 12:3. The addition of SiC whiskers was critical for the multi-reflection, interfacial polarization and dielectric attenuation of EM waves. A multilayer composite with a gradient change from transmission to reflection of RGO@SiC porous films was constructed. The highest SE_T reached 75.1 dB with a SE_R of 2.7 dB for a film of a thickness of about 1.5 mm when the reflective side of the multilayer composite was stacked on a reflective buckypaper derived from multi-walled carbon nanotubes. We believe that the porous RGO@SiC thin films were promising for designing a multilayer or sandwich structure for EMI absorption in packaging or lining.