Wheat ash ash silica (WHA) aerogels were prepared by a sol-gel process by drying under ambient pressure. The silica was extracted from WHA by a NaOH solution to form sodium silicate, which was used as a precursor for aerogels. The wet silica gels were synthesized by resin-alkali exchange catalysis of the sodium silicate solution, followed by solvent exchange with ethanol (EtOH) and hexane in turn. Accordingly, a mixture of trimethylchlorosilane, EtOH and hexane was used for surface modification of the wet gels in order to obtain hydrophobic silica aerogels. The density, pore structure, hydrophobic property and thermal insulation property of the obtained silica aerogels were investigated in detail. The results show that the formation of silica aerogels can be successfully performed in a weight ratio SiO 2 / H 2 O ranging from 0.065 to 0.167. Silica aerogels have a desirable pore structure with a surface area ranging from 513 ± 5 to 587 ± 6 m2 / g, a pore volume of 2.3 ± 0.3 to 4.0 ± 0.1 cm 3 / G and a pore size of 9 ± 2 to 15 ± 1 Nm, an outstanding hydrophobic property having a water contact angle of 147 ± 0.1 ° and a distinguished thermal insulation property with a low thermal conductivity ranging from 0.009 ± 0.0001 to 0.012 ± 0.0002 W / (m · K).