<p>Structure modulation at multiscale is crucial for optimizing the electromagnetic wave absorption (EWA) properties of fiber-reinforced composites. Here we selected two types of wave-absorbing SiC fibers as reinforcements. The L-fiber had a relatively low resistivity of ∼3 Ω·cm and the H-fiber had a high resistivity of ∼7×10⁵Ω·cm. To adjust the impedance, BN single coating and SiO₂/BN dual-coating were prepared respectively on the L-fibers. Unidirectional prepregs with different fibers were stacked in different rules to obtain the final composites. It showed that both the fiber coatings and stacking structure significantly influence the EWA performance of the composites. Guided by computational optimization, the stacked composites exhibited superior reflection loss (RL) lower than −10 dB across the whole X (8.2–12.4 GHz) and Ku (12.4–18.0 GHz) bands. It is interesting to find that the introduction of the surface coatings on the L-fibers significantly widens the available thickness range of the stacked composite for possessing excellent performance. In particular, dual-coating perform better in terms of broadening the available thickness range of the stacked composites.</p>