A new type of microwave absorbing material (TCF@Fe3O4@NCLs) with multi-layer heterostructure is designed and fabricated via a one-step pyrolysis process of the precursor (PF@Fe3O4@PDA). PF@Fe3O4@PDA is prepared by the technology of confined self-polycondensation, solvothermal method coupled with polymerization of dopamine (DA). The as-obtained material has the structure of tubular carbon nanofibers (TCF) embedded with Fe3O4 nanoparticles, dispersed Fe3O4 nanoparticles, and nitrogen-doped carbon layers (NCLs) from inside to outside. Notably, tubular carbon nanofibers provide the major dielectric loss. Fe3O4 nanoparticles significantly improve the microwave absorption ability at low frequencies and provide appropriate magnetic loss. NCLs improve the conductivity and facilitate the generation of multiple polarization effects, resulting in enhanced dielectric loss. The absorption mechanism is further elucidated. Based on the synergistic effect of double dielectric/magnetic loss composite materials, the interface introduced by multi-layer heterostructure, and conductive networks, TCF@Fe3O4@NCLs exhibits excellent reflection loss (RL) of -43.6 dB and effective absorption bandwidth (EBA) of 4.6 GHz (8.2-12.8 GHz) with a loading of 10%. The results demonstrate potentially promising prospects of TCF@Fe3O4@NCLs as new material candidate for microwave absorption. (C) 2020 Elsevier Inc. All rights reserved.