Abstract: The coupled numerical method for thermochemical non-equilibrium ablation flow and structural thermal field was established for the carbon based material ablation phenomenon of spacecraft reentry. A chemical reaction model and a heat conduction model were utilized for the simulation of a flow field and a structural field, respectively. After the verification of simulation models, a three-dimensional ball head ablation reaction was simulated to obtain the time progress of structural heat conduction, and the ablation flow field parameters were studied. The results show that the ablation effect has an influence on the distribution of chemical constituents in flow field and increases the shock detached distance as well. The results can be used in engineering applications.