Abstract: To solve the problem of electromagnetic radiation pollution, it is necessary to develop an economic and environmentally friendly way of producing efficient electromagnetic wave absorbing materials. Carbon-based materials have attracted much attention but finding suitable precursors and ways of producing defined pore structures are still challenges. We reporte a simple method to produce porous carbon using coal liquefaction oil residue as the carbon source. The produced porous skeletons are due to the Na₂CO₃ templates and CO₂ gas generated during the thermal decomposition of NaHCO₃ templates. It is found that changing the pore structure not only adjusts the impedance matching of the material but also increases the length of the electromagnetic wave transmission path and increases dielectric loss. With the combined effect of multiple electromagnetic loss mechanisms, the material has excellent electromagnetic wave absorption. Specifically, with a filler loading of only 10% and a thickness of 2.03 mm, the obtained carbon material has a reflection loss value of −60.28 dB and an effective absorption bandwidth of 5.36 GHz. This work provides a new approach to developing high-performance carbon-based electromagnetic wave absorbing materials and also offers a new idea for the high value-added use of coal liquefaction oil residue products.