Abstract: SiO₂ aerogel insulation composites were prepared by impregnating inorganic ceramic fiber with SiO₂ sols results via supercritical drying. The effect of SiO₂ sol on mechanical properties of the composites was investigated. The results show the higher the ethanol (EtOH) content in sol, the lower the density of aerogel, the bigger the average pore size, the less the cross-linking between the clusters and the lower the network strength of aerogel. The inorganic ceramic fibers are dispersed within the aerogel and closely packed by aerogels, thus a well interface is formed. With increasing the EtOH/TEOS molar ratio from 2 to 20, the load transfer capability of SiO₂ aerogel is weakened, therefore, the mechanical properties of the aerogel composites decrease. The tensile, bending and compressive strengths of the composites decrease from 1.9MPa, 2.7MPa, 1.73MPa (10% strain) to 0.17MPa、 0.12MPa、 0.04MPa (10% strain), respectively.