<p>SiO₂ aerogel has broad application prospects in thermal insulation fields such as aerospace, industrial energy conservation, and building energy saving. However, the high preparation cost and poor high-temperature stability limit its large-scale industrial production and application. Herein, CaSO₄-modified SiO₂ aerogel (SC) with low cost and high thermal stability was synthesized from water glass and CaSO₄ via the sol-gel and supercritical drying route. The effect of CaSO₄ doping amount on the morphology, pore structure and physical properties of SC was investigated. Results show that the effective doping of CaSO₄ can significantly improve the heat resistance ability of SC at the temperature of 800–1000 ℃. After heated at 800 ℃ for 2&#xa0;h, the weight loss of the modified aerogels was less than 7%, and the volume shrinkage rate was as low as 4%. The specific surface area of SCs (≥ 166 m²/g) after calcined at 1000 ℃ for 2&#xa0;h were higher than that of the unmodified aerogels (119 m²/g). Mechanism analysis shows that not only Ca²⁺ can replace the active group Si-OH on the surface of the gel, reducing the intrinsic surface energy and sintering driving force of the gel particles and but also the Ca₂SiO₄ second phase is generated during the heating process, which hinders the contact growth of the particles and further improves the temperature resistance of the aerogel. These findings propose feasible ideas and methods for the application of SiO₂ aerogel materials in high-temperature thermal insulation.</p>