Abstract: In this paper, a simplified model is built for simulating the sound wave skimming over a high-temperature insulation specimen in the thermal-acoustic testing for studying the influence of the temperature boundary layer on the sound field near the wall. The integration method is used to obtain the temperature distributions in the thermal boundary layer when the room temperature gas sweeps past the high temperature wall. Based on that, the finite difference method is used to solve the scatting problem of the plane wave propagation in an inhomogeneous medium, and the sound pressure distribution near the wall of the high-temperature flat plate is calculated. It is shown that the temperature boundary layer attenuates the sound field near the wall. When the frequency is 10 000 Hz, the sound pressure level in the near wall region is reduced by about 3 dB compared with the case without the temperature boundary layer. The result may provide some reference for adjusting or correcting the real test parameters.