Abstract: In order to study the effect of ablation time on the ablation mechanism of C/C-SiC composites under a hypersonic oxygen-rich environment, the dynamic ablation mechanism of the needled carbon/carbon-silicon carbide composites prepared by “chemical vapor infiltration + precursor immersion pyrolysis” hybrid process was studied by the hypersonic oxygen-enriched ablation test technology in this paper, and the ablation surface morphology of the composites were investigated by scanning electron microscopy. The results show that, the C/C-SiC composites can resist the oxidation working environment of high temperature, high pressure and hypersonic gas jets in a short time under the extremely harsh hypersonic oxygen-enriched ablation environment. The mass ablation rate of C/C-SiC composites after 10 s, 20 s, 30 s, 40 s and 50 s ablation by hypersonic oxygen-enriched ablation are 0.021 g/s, 0.025 g/s, 0.027 g/s, 0.026 g/s and 0.034 g/s, respectively. The dynamic ablation behavior of the C/C-SiC composites under the hypersonic oxygen-enriched environment is synergistic effects of thermo-oxidation ablation and mechanical erosion. In the initial stage, the existence of the SiO₂ protective film effectively prevents the diffusion of oxidizing components into the matrix, and only the central area of the material is slightly thermal oxidative ablation. In the middle test, the ablation of the material is mainly manifested in the combined effect of thermo-oxidation ablation and mechanical erosion, and gradually transition from mainly thermal oxidative ablation to mainly mechanical erosion. In the later stage of the ablation test, the further reaction of the matrix makes the ablation mechanism of the material mainly manifested as the large-area flaking of the fiber and matrix.