The invention relates to a method for preparing an aerogel composite thermal insulation felt through normal pressure drying. The specific steps comprise: uniformly mixing a silicon source and deionized water to obtain a silicon-containing solution, uniformly mixing the silicon-containing solution, ethanol and an acidic catalyst, and stirring to obtain a sol; placing a composite material in a container, injecting the sol into the container loaded with the composite material, heating, and carrying out thermal insulation so as to wait gelation; placing the gel composite body obtained after the gelation into an acid alcoholization solution obtained by mixing anhydrous ethanol and sulfuric acid, heating, and carrying out thermal insulation; placing the gel composite body into a modified solution obtained by mixing a hydrophobic modifier and a solvent; and carrying out normal pressure drying on the modified gel composite body to obtain the aerogel composite thermal insulation felt material.According to the present invention, the technical scheme has advantages of low cost, less steps, less gel impurities, less energy consumption, simple equipment operation, and simple equipment maintenance.