Optimizing the electromagnetic (EM) properties of composites through elaborate tailoring of their microstructures has become an attractive research branch, but determining the correlations between morphology, composition, and performance remains challenging. Herein, a novel progressive hollow engineering strategy is proposed for the construction of hollow CuFePBA (CF) precursors with asymptotic variations of cavities and Prussian blue analog (PBA) units based on a synergistic etching-assembly approach, subsequently combined with a polydopamine (PDA) coating and carbothermal process to acquire raspberry-like hollow Cu/Fe/Fe3C@NC (CFC) composites. The proposed approach addresses the drawbacks caused by organic ligand depletion or corrosive agent usage. We then present a systematic investigation of the mechanism by which the progressive hollow engineering-induced concurrent evolution of hollow cavities, phases, defects, and inhomogeneous interfaces contributes to the improvement of the dielectric properties of the CFC samples. An optimal reflection loss (RLmin) of − 60.42 dB at 3.29 mm was realized for the CFC-2 sample and the CFC-3 sample achieved an effective absorption bandwidth (EAB) of 4.4 GHz at an ultra-thin thickness of 1.29 mm. This work reveals the synergistic effects of compositional, interfacial, and defect variations on the EM wave attenuation properties of the composites, and will provide new design inspiration for novel absorbers with modulatable hollow architectures.