Abstract: In order to meet the thermal and drag reduction requirements of high speed vehicles in near space, three-dimensional numerical simulation method was used to study the typical lift-body vehicle in near space. The aerodynamic thermal characteristics of the vehicle were analyzed, and the law and mechanism of mass ejection on the aerodynamic thermal characteristics were analyzed. The results demonstrate that wall mass ejection can slightly increase the detachment distance of the shock wave, thicken the shock wave layer and velocity boundary layer, and reduce the velocity gradient within the boundary layer, resulting in satisfactory drag reduction performance. For a typical lifting body configuration, wall mass ejection can reduce skin friction by more than 47.5% at flight altitudes ranging from 60 km to 70 km, while 10.2% at 80 km altitude. The drag reduction effect of wall mass ejection is enhanced with the increase of the attack angle, while weaken with the increment of flight altitude. Wall mass ejection not only thickens the temperature boundary layer but also provides thermal protection by ejecting low-temperature gas, which can significantly reduce the skin heat flux on the windward side.