Abstract: The gas injection effect is the main heat dissipation mechanism of ablative materials, which would significantly affect the thermal insulation characteristics of ablative thermal protection systems. Based on the shock tube wind tunnel, the experimental study on the influence of gas injection on downstream aero-heating was conducted. The influence of factors such as gas injection, mainstream Mach number, Reynolds number was obtained. Combined with numerical simulation results, the correlations of the influence of gas injection on aero-heating were obtained under laminar and turbulent boundary layer flow conditions. The cooling efficiency of gas injection for laminar boundary layer is remarkable. The maximum cooling efficiency for laminar boundary layer is close to 100% when the blowing ratio F=0.483%. The cooling efficiency would decrease sharply when the boundary layer transition occurs because of the strong mixing effect of turbulent boundary layer. The larger the specific heat capacity of cooling gas, the better the cooling effect.