The speed of sound in silica aerogel is a critical parameter in the test of the mechanical and thermal properties. The solid thermal conductivity and elastic modulus of the silica aerogel can be calculated directly from the sound speed formulas without additional measurement costs. However, it is difficult to obtain the sound speed of the aerogel at high temperature directly through the measurements. In this work, we proposed an approach to obtain the elastic modulus of silica aerogel at high temperature from the theory of minimum thermal conductivity including Cahill model and Diffusons model. The method is firstly to test the solid thermal conductivity of the silica aerogel for predicting the sound speeds in the aerogel at high temperature, and then use the elasticity sound speed model to calculate the elastic modulus. Since the thermal radiation effect cannot be neglected at high temperature, the solid thermal conductivity of aerogel at high temperature is equal to the difference between the solid thermal conductivity under vacuum environment and the radiative thermal conductivity. Firstly, the experimental data of the solid thermal conductivity of silica aerogels with different densities at room temperature are employed and the obtained elastic modulus is fitted as a power-law exponential function of the density. Five groups of available experimental data are also employed to validate the present fitting relations, and good agreement is found for the silica aerogel in the density range of 75−400 kg/m³ with corresponding elastic modulus in the range of 0.48-122.41 MPa. The experimental data of the solid thermal conductivity of silica aerogel with a density of 150 kg/m³ in the temperature range of 300-550 K are employed for the temperature-dependent elastic modulus tests. A group of available experimental data is introduced to validate the calculations of the temperature-dependent elastic modulus of the silica aerogel, it is found that the calculated temperature-dependent elastic modulus based on the Cahill model is more consistent with the experimental data.