Abstract: To improve the anti-ablative performance under high pressure heat fluxes environment, an enhancement method was presented for ZrB₂/SiC composite coatings on the C/C matrix. It was arranged like that, taking the chemical vapor deposition as the preparation method of sealing layer (CVD)–SiC on the plasma spraying ZrB₂/SiC composite coatings and taking the CH₃SiCl₃–H₂–Ar as a deposition system. Based on this condition, the structure evolution of the ZrB₂/SiC composite coatings with CVD–SiC sealing layer and ablation property and ablation mechanism were investigated under an oxyacetylene torch environment. The results show that after two 600 s cycles ablation, the ZrB₂/SiC composite coating enhanced by the CVD–SiC sealing layer still possesses the ablative resistance and the surface of CVD–SiC shows a transformation from β to α phase. CVD–SiC layer is filled with the gap of plasma spraying ZrB₂/SiC composite coatings, the sealing layer can restrict the oxygen diffusion to the C/C matrix along cracks and holes in the coatings, thereby improving the ablative resistance.