step 1: without considering a shape deformation of an aircraft caused by an ablation retreating effect, according to a hypersonic incoming flow far-field boundary condition to be studied, performing a numerical simulation of a non-deformation hypersonic aircraft external flow field by using a macro Computational Fluid Dynamics (CFD) solver;

step 2: after a macro CFD calculation of a non-deformation hypersonic aircraft converges, extracting mass fractions and temperatures of wall surface components in a high-temperature area through a post-processing software Tecplot, averaging the mass fractions of the wall surface components to obtain an average wall surface component mass fraction, averaging the temperatures of the wall surface components to obtain an average wall surface temperature, and inputting the average wall surface component mass fraction and the average wall surface temperature into a micro Reactive Molecular Dynamics (RMD) solver;

step 3: performing micro modeling on a gas-solid interface of a target ablation heat resistant material according to a density and a material elemental composition, thereby obtaining a micro model of the target ablation heat resistant material; performing numerical simulation on the micro model through a micro RMD solver, wherein a heating temperature is consistent with the average wall surface temperature of the high-temperature area obtained by the macro CFD calculation; impacting a solid-phase atomic model in the micro model by taking the average wall surface component mass fraction obtained by the macro CFD calculation as an incidence ratio of molecules and atoms, thereby obtaining a msd.txt file for recording mean square displacement data and an atomic path files;

step 4: when the micro model becomes stable, calculating a system diffusion coefficient by means of a Mean Square Displacement (MSD) method, and counting densities of an original solid phase of the target ablation heat resistant material in different areas along a diffusion direction, thereby obtaining a slope factor of a density variation with a distance along the diffusion direction, and obtaining a mass loss rate by means of a Fick's law, wherein a ratio of the mass loss rate to an original density of the target ablation heat resistant material is an ablation retreating rate;

step 5: inputting the ablation retreating rate obtained by the micro method into the macro CFD solver, and performing a grid reconstruction and a transient calculation using an user-defined module (UDF) by taking the ablation retreating rate obtained by the micro calculation as a basis of a wall surface grid movement, thereby obtaining a transient variation of a hypersonic aircraft external flow field along a variation of an ablation retreating of a wall surface of the aircraft.