The mineralization and sintering behaviors of SiO₂ gels were investigated. After calcined at 500 °C, the decomposition of Si-OH in the amorphous gels accomplished. As the temperature continued rising, crystallinity of the products strengthened grdually. After calcined at 1400 °C, cristobalite was separated out from amorphous SiO₂. As sintering temperature increased, relative density, elastic modulus and hardness of SiO₂ ceramics were all increased gradually. Three-dimensional aluminosilicate fiber-reinforced silica matrix composites were fabricated by sol-gel process. Effects of sintering temperature on the density, microstructure and mechanical properties of the composites were investigated. The composites prepared at 900 °C displayed the highest mechanical properties. The average flexural strength, interlaminar shear strength and fracture toughness of those composites, with the density of 1.97 g/cm₃, were 119.7 ± 7.5 (MPa)、10.8 ± 0.7 (MPa) and 4.0 ± 0.4 (MPa.m_1/2), respectively. Moreover, as sintering temperature increased, the pullout fiber shortened gradually and eventually disappear at the composite fracture surface.