Abstract: To investigate the effects of oxyacetylene ablation test parameters and multiphysics distribution on the ablation mechanism of C/C composites, an ablation model was developed based on the oxy-acetylene ablation method. The temperature field, flow field, and chemical reaction field during the ablation process were simulated using multiphysics coupling simulation technology. The ablation morphology was observed via scanning electron microscopy, and combined with the simulation results, and the ablation mechanisms under different test conditions were elucidated. The research demonstrates that the temperature field distribution obtained from the multiphysics coupling simulation of oxy-acetylene ablation of C/C composites exhibits a high degree of consistency with experimental results. The gas flow rate on the ablated surface of the specimen initially increases and then decreases from the center to the edge. The mass fractions of reactive gases at ablation distances of 10 mm and 20 mm exhibit two non-linear changes. Thermochemical ablation predominates in the central ablation region of C/C composites. Among them, thermal oxidation by O₂ is the primary process at an ablation test distance of 10 mm, while thermal oxidation by H₂O/O₂ dominates at distance of 20 mm. Mechanical erosion by high-speed gas flow is predominant in the transition ablation region, supplemented by thermal oxidation from H₂O/O₂. Thermal oxidation by H₂O and etching by H₂ are dominant in the edge ablation region, with mechanical erosion by gas flow playing a secondary role.