Heterointerface engineering has drawn considerable interest in tuning interfacial polarization and promoting impedance matching. Therefore, it has become a key strategy for optimizing electromagnetic wave (EMW) absorption. This comprehensive review primarily focused on the EMW absorbing strategies of polymer-based materials, emphasizing the critical developments of heterointerface engineering. A possible EMW absorbing mechanism of polymer-based materials was proposed, emphasizing the synergism of multi-components, microstructure design, and heterointerface engineering. Key innovations in structural design such as porous structure, multilayered structure, and segregated structure are explored, highlighting their contributions to enhancing EMW absorption. Also, the review highlights the latest research progress of advanced conductive polymer-based and insulating polymer-based materials with desirable EMW absorption performance; their fabrication methods, structures, properties, and EMW absorption mechanisms were elucidated in detail. Key challenges on polymer-based EMW absorbing materials are presented followed by some future perspectives.