The invention belongs to the technical field of heat insulation and preservation materials applicable to semiconductor preparation, and particularly relates to a silica-based Si-C-O aerogel heat insulation composite material and a preparation method thereof. According to the preparation method of the silica-based Si-C-O aerogel heat insulation composite material, firstly, a silicon source and a carbon source are mixed and subjected to a reaction, and accordingly sol of a nanometer porous three-dimension network framework structure is obtained; short silica fibers are used as raw materials and subjected to fiber slurry suction filtering and compression molding, and a porous fiber prefabricated part is obtained through high-temperature sintering; then the sol and the silica porous fiber prefabricated part are combined to form a mixture of silica fibers and Si-C-O aerogel; supercritical fluid drying is carried out on the mixture to obtain a Si-C-O aerogel precursor composite material of a nanometer porous structure; and the Si-C-O aerogel precursor composite material is subjected to high-temperature inert atmosphere pyrolysis, and finally the silica-based Si-C-O aerogel heat insulation composite material is obtained. The silica-based Si-C-O aerogel heat insulation composite material integrates the Si-C-O aerogel and the silica fibers, is excellent in performance, and is suitable for the semiconductor manufacturing industry.