The invention discloses a silicon dioxide aerogel coating and a preparation method thereof. The coating is prepared from the following ingredients in parts by weight: 100 parts of silicon dioxide wetgel, 20-50 parts of auxiliary film forming matter, 0.3-0.5 part of mildewproof microbicide and 0.1-2.0 parts of thickening leveling agent. The preparation method comprises the steps of weighing the silicon dioxide wet gel, adding the auxiliary film forming matter, the mildewproof microbicide and a thickener at a low speed with low-speed stirring, carrying out stirring for 30 minutes or more, adding a proper volume of distilled water or deionized water, and adjusting the viscosity of the coating to about 1,500mPa.s, thereby obtaining the finished coating. According to the silicon dioxide aerogel coating and the preparation method thereof, concentrated aerogel colloid is directly used as a raw material, thus, the difficult dispersity of aerogel powder materials is avoided, and the possibility of structural damage to aerogel powder after secondary water absorption is also avoided; meanwhile, through adding a structural stabilizer, the problem of structural collapse during drying is overcome, and a reinforcing effect in a later-stage film forming process can also be achieved; and the coefficient of thermal conductivity of a coating film at normal temperature can reach 0.015W/m.K to theminimum, and the light transmittance of the coating film can reach 80% or above.