SiO2 aerogel thermal insulation composites have been widely used in aerospace, petrochemical and other thermal insulation fields, and their application can be significantly expanded through hydrophobic modification. In order to maintain good hydrophobic properties of SiO2 aerogel thermal insulation composites at high temperature, polysiloxane modified silicate coatings were used to modify the surface hydrophobicity of SiO2 aerogel thermal insulation composites by brushing. The effect of coating thickness on crack expansion was then investigated, as well as the failure mechanism of hydrophobic properties of the coating at high temperature and the wear resistance of the composite before and after brushing coating modification. The results show that the surface of the coating is crack-free and the contact angle reaches (113±2)° when the coating thickness is about 13 μm. The contact angle still is maintained at 105° after heat treatment at 450 ℃ for 1 800 s, showing good thermal stability. Meanwhile, the coating significantly improves the wear resistance of composites.