This study investigates the impact of the high-temperature effect, esp. the real gas effect and the chemical reactions, on hypersonic aerothermodynamic solutions and the aerothermoelastic behavior of a typical skin panel in hypersonic flow. First, several computational fluid dynamics codes that were developed in significantly different ways were benchmarked and compared for hypersonic aerothermodynamics, emphasizing the impact of high-temperature effects as well as turbulence modeling on heat flux prediction. Subsequently, a reduced-order model (ROM) for hypersonic aerothermal loads accounting for the high-temperature effect is developed. Particularly, a ROM correction approach for high-temperature effect was presented, so that a ROM constructed based on the perfect gas assumption can generate fluid solutions that account for the real gas effect with reasonable accuracy. Finally, the new fluid ROM was applied to study the impact of the high-temperature effect on the aerothermoelastic response of a hypersonic skin panel, with an emphasis on its stability boundary.