Abstract: The high crystalline single-walled carbon nanotubes(SWCNTs) were prepared by direct current arc-discharge method and the CoFe₂O₄ nanoparticles were prepared by sol-gel method. The double-layer composites for microwave absorption were fabricated by compositing SWCNTs and CoFe₂O₄. Their phase structures, surface morphologies and electromagnetic parameters were characterized by Raman spectrum, XRD, SEM, TEM and vector network analyzer. The microwave absorption properties of SWCNTs-CoFe₂O₄ double-layer composites were calculated according to transmission line theory in the frequency range of 2-18 GHz. The results show that the absorption property of SWCNTs-CoFe₂O₄ double-layer composites is improved greatly. The best reflection loss of SWCNTs-CoFe₂O₄ double-layer composite reaches -61.13 dB as the match layer is CoFe₂O₄ and the absorbing layer is SWCNTs. The absorbing bandwidth with the reflection loss values below -10 dB of SWCNTs-CoFe₂O₄ double-layer composites is 7 GHz which from 8 GHz to 15 GHz. SWCNTs-CoFe₂O₄ nanoparticles double-layer composites could be described as an excellent absorbing material with high reflection loss and broad absorbing bandwidth.