The invention discloses a silicon dioxide aerogel with a high specific surface area and a fast preparation method thereof. The preparation method comprises the following steps: cooling all raw materials, in a cooling condition, mixing a silicone precursor, a solvent, an acidic catalyst and water, then adding an alkaline catalyst and a reaction accelerant, leaving the mixture to stand to gelatinize the mixture, and aging the mixture in the condition; transferring the aged gel into an exchange liquid to be soaked for solvent exchange; and performing supercritical drying on the gel after solvent exchange to obtain the silicon dioxide aerogel. By adopting a mode of cooling preparation, collapse of holes of the aerogel in a nano-structure due to solvent evaporation in the preparation and gel aging processes is avoided, and meanwhile, by using the reaction accelerant, the reaction rate at a low temperature is accelerated and the preparation efficiency is improved. In addition, an exchange liquid is used to replace the solvent in the surface layer of the gel before supercritical drying, so that the damage of the aerogel structure due to solvent evaporation in the temperature-raising and pressure-raising process is reduced, and the prepared silicon dioxide aerogel has a good specific surface area.