Abstract: The pervasive adoption of 5th generation mobile communication technology propels electromagnetic wave (EW) absorbents to achieve high-level performance. The heterointerface construction is crucial to the improvement of absorption ability. Herein, a series of ultralight composites with rational heterointerfaces (Co/ZnO@N-doped C/layer-stacked C, MSC) is fabricated by calcination with rational construction of sugarcane and CoZn–zeolitic imidazolate framework (ZIF). The components and structures of as-prepared composites were investigated, and their electromagnetic parameters could be adjusted by the content of CoZn–ZIFs. All composites possess excellent EW absorption performance, especially MSC-3. The optimal minimum reflection loss and effective absorption band of MSC-3 can reach −42 dB and 7.28 GHz at the thickness of only 1.6 mm with 20wt% filler loading. This excellent performance is attributed to the synergistic effect of dielectric loss stemming from the multiple heterointerfaces and magnetic loss induced by magnetic single Co. The sugarcane-derived layer-stacked carbon has formed consecutive conductive networks and has further dissipated the electromagnetic energy through multiple reflection and conduction losses. Moreover, the simulated radar cross section (RCS) technology manifests that MSC-3 possesses outstanding EW attenuation capacity under realistic far-field conditions. This study provides a strategy for building efficient absorbents based on biomass.