Abstract: Monolithic alumina-based aerogels are prepared by sol-gel method and ethanol supercritical supercritical drying process with aluminum sec butanol as precursor, nitric acid as catalyst and trimethylethoxysilane as silica modifier. The mollite fiber reinforced alumina-based aerogel composite is successfully prepared by making the alumina-based aerogel solution permeated into the mullite fiber, then the TiO₂/ mollite fiber/ alumina-based aerogel composite is prepared by adding TiO₂ powders. The structures and thermal properties of the three aerogels are characterized. The results show that suitable addition of trimethylethoxysilane can obviously improve the heat stability of the aerogel. The TiO₂/ mollite fiber/ alumina-based aerogel composite possesses excellent heat stability and thermal insulation performance, and proves to be a high-efficient thermal insulation material with practical value.