The development of electromagnetic (EM) wave-absorbing materials is crucial for applications spanning information communication, equipment protection, and advanced defense systems. As operational environments extend toward high-speed and high-temperature regimes, a distinct class of high-temperature wave-absorbing materials has emerged, where EM response is no longer governed solely by intrinsic material properties but is strongly coupled with thermal activation effects and phase instability. The purpose of this review is to establish a comprehensive understanding of the key factors that govern high-temperature wave absorption and to identify design principles that can bridge intrinsic EM optimization with practical service reliability. First, this review clarifies the temperature-dependent evolution of intrinsic EM parameters, especially the loss of magnetic response above the Curie temperature, the drift of complex permittivity, and the resulting conflict between impedance matching and dielectric attenuation. Strategies for temperature-insensitive and broadband absorption are then discussed, including interfacial-polarization regulation, positive/negative temperature coefficient compensation of conductivity, frequency dispersion regulation, macrostructural resonance, and multiscale collaborative design. Second, the effect of oxidation, phase transformation, and decomposition, thereby introducing performance instability beyond idealized material assumptions, on the intrinsic EM responses are discussed. Then, the multi-physics coupling regime (thermal-mechanical-oxygen fields) encountered under near-service conditions is highlighted, where structural integrity degradation and EM attenuation failure become intrinsically intertwined, representing a system-level challenge that cannot be addressed by single-factor optimization. The oxidation-resistant design strategies for integrated load-bearing and wave-absorbing ceramic matrix composites, as well as design methods and recent progress related to high-temperature wave-absorbing coatings, are reviewed. Finally, remaining challenges and future development directions for high-temperature wave-absorbing materials are discussed.