Developing electromagnetic wave (EMW) absorbers with low-cost, lightweight, strong absorption capacity, thin matching thickness, and wide effective absorption bandwidth (EAB) is still a significant challenge. Herein, we report a unique g-C₃N₄/Fe₃CNC/Co-NC heterostructure by simple mixing and two-step pyrolysis of melamine, Fe₃O₄, and ZIF-67. After the structural and phase reconfiguration, N-doped carbon layer-coated Fe₃C nanoparticles (NPs) assembled nanoshells (Fe₃C@NC) and N-doped graphitic carbon-coated metallic Co NPs (Co@NC) are formed, and the core-shell NPs are interconnected by porous g-C₃N₄ bridges. Profiting from the successful construction of the unique g-C₃N₄/Fe₃CNC/Co-NC heterostructure and the synergetic effect of multi-component, multiple core-shell structure, and strong interaction, the as-fabricated g-C₃N₄/Fe₃CNC/Co-NC inherits the excellent EMW absorption performance with a R_L value of -25.4 dB at a thin matching thickness of 2.6 mm. The EAB can reach up to 8.64 GHz at a thickness of 2∼5 mm. This study provides the contribution of structural and phase reorganization to the field of EMW absorption.