Abstract: During high-speed flight of reentry spacecrafts, the vehicle surface is subjected to an intense aerodynamic heating, resulting in the formation of a complex high-temperature gas environment that may cause sever damages to the vehicle materials and affect the reliability of the vehicle structures. Therefore, in order to facilitate thermal protection testing of reentry vehicles, it is of great importance to develop the ground simulation facilities to simulate the surface thermal environment during the reentry process of high-speed spacecrafts. In this paper, the influences of operating pressure on the energy transport processes and the plasma gas temperatures are analyzed based on numerical modeling; and consequently, a novel method for modulating the heat flux density to a surface is proposed by changing the operating pressures. Based on this modulation method and by using the principle of matching the heat flux density and heating time with the real flight conditions, a large-volume high-temperature arc plasma jet with a wide range of adjustable heat flux density is generated on a six-phase alternating-current arc plasma experimental platform; and the surface thermal environment of the reentry vehicles is successfully simulated in the ground laboratory. Then, the ground ablation experiments of phenolic impregnated carbon ablator are conducted. The experimental results under the surface heat flux densities ranging from 1.07 to 3.95 MW/m² are in good agreement with the published data in the literature, which validates the reliability of the ground simulation method developed in this study. Finally, the materials surface ablation experiments for typical components of a high-speed reentry aircraft are conducted. Under the experimental conditions with the highest heat flux density up to 5 MW/m², the obtained results from the ground simulation experiments are in good agreement with the corresponding real flight data. This indicates that the ground laboratory simulation method proposed in this paper can, to some extent, simulate the surface thermal environment during the aircraft reentry process without the need of using a high-cost wind tunnel.