Abstract: Fiber-reinforced aerogel composites have emerged as promising materials for extreme high-temperature environments due to their excellent thermal insulation, low density, and structural stability. This paper systematically reviewed the preparation methods, microstructure regulation strategies, and synergistic mechanisms for thermal insulation and flame retardancy. It was found that the selection of fiber types combined with interface modification significantly enhanced mechanical properties and thermal stability. By optimizing drying processes, the pore structure was tailored, achieving thermal conductivity as low as 0.018-0.065 W/(m·K). The multiscale structure—nanopores limiting gas conduction, micro-fibers providing skeleton support, and infrared opacifiers reducing radiative heat transfer-along with organic-inorganic hybrid precursors, collectively contributed to superior high-temperature performance. These materials exhibit broad application potential in aerospace thermal protection, building energy efficiency, and power battery thermal management. Future research should focus on multiscale simulation, smart functional coatings, and green manufacturing processes to facilitate industrial applications.