Silica-doped alumina aerogels offer the potential alternative to the applications as thermal insulators, catalysis, or catalytic support at elevated temperatures. However, the production process of silica-doped alumina aerogels was complicated and time-consuming. We developed a one-step precursor-to-aerogel method of silica-doped alumina aerogels with high specific surface area and thermal stability. Compared to conventional methods, the developed method reduced time and solvent waste of alumina-based aerogels production. Here, we investigated the alumina aerogels doped with silica to stabilize γ-phase at higher temperatures. XRD, FTIR, TEM, TG-DSC, and BET analysis results showed that silica stabilized the γ-Al₂O₃ at 1200 °C. The stabilization mechanism analysis showed that silica addition could significantly hinder the contact among alumina particles and the formation of necks in the sintering process, thereby retarding the transition of γ–θ phase and maintaining the high specific surface area at elevated temperatures. Silica and alumina particles formed mullite at 1200 °C, which could suppress α-phase transformation. In addition, silica-doped alumina aerogels exhibited the high specific surface area of 311 m²/g at 1000 °C and 146 m²/g at 1200 °C when the silica content was in the range of 10.6–13.1 wt%.