Abstract: For air-breathing high-speed vehicles, inner and outer flows are highly coupled and there are strong interactions between shockwaves and boundary layers. Boundary layers are sensitive to the variation of the wall temperature, so do the aerodynamic characteristics. Consequently, how to predict the wall-temperature effect exactly and improve the prediction accuracy of aerodynamic characteristics are important for the design of high-speed vehicles. In this article, the effect of the inner flow wall temperature on aerodynamic characteristics is investigated through wind-tunnel measurements and numerical simulations. Results show that in conventional hypersonic wind tunnels, the inner wall temperature of the high-speed vehicle model increases continuously with the wind-tunnel running time, yielding significant variations of the pitching moment and wall pressure. The maximum increment of the pitching moment requires an increase of the rudder angle by 2°. In addition, numerical simulation results indicate that the thickness of boundary layer in the internal flow increases with the rise of wall temperature. Moreover, the equivalent area of high-speed flow channel decreases so that the flow is compressed. The change of velocity profiles in boundary layers results in the forward moving of shockwaves in the internal flow channel, which causes the change of pitching moment of high-speed vehicles.