A preparation method of SiO2 aerogels is for solvent replacement process during preparation of SiO2 aerogels and adopts “a manner of continuously circulation filtration” for an operation of adding solvent so that wet gel is continuously circulated and replaced (rinsing) by mass alcohol solvent and organic solvent to greatly accelerate (reducing) the time for replacement operation of wet gel solvent. At the same time, the alcohol solvent or the organic solvent passing through the reaction container separates wet gel from water content or the alcohol solution through filtration procedure. Afterward the alcohol solution and the organic solution enter the reaction container to perform solvent replacement such that fast continuously circulation filtration is performed to greatly improve the effect of replacing wet gel solvent.