In order to improve the ablation resistance of carbon-based materials in elevated-temperature and oxygenated environments, Ti-doped HfB₂-SiC and ZrB₂-SiC composite coatings were prepared on the surface of graphite via a hybrid method involving slurry dipping and reactive infiltration. Phase compositions, microstructures, and element distributions of the composite coatings were studied, and anti-ablation ability of the coating was evaluated at 2300 ℃. Results show that structures of Ti-doped Hf(Zr)B₂-SiC composite coatings are very dense after silicon infiltration. Both HfTiB₂ and ZrTiB₂ ceramic phases are embedded in the coatings, which exhibit no defects and establish robust bonds with the graphite substrates. Residual silicon continuously distributes around Hf(Zr)B₂ and SiC particles. After undergoing ablation at 2300 ℃ for 480 s, the mass ablation rates of HfTiB₂-SiC and ZrTiB₂-SiC composite coating samples are -2.71×10^-3 and -4.20×10^-1 mg/s, respectively, indicating a slight weight gain. The corresponding line ablation rates are 1.88×10^-4 and 3.70×10^-4 μm/s, respectively. Following ablation, a Hf-Ti-Si-O multiphase oxide layer composed of HfTiO₄-HfO₂ as the skeleton and TiO₂-SiO₂ as the filling phase forms on the surface of HfTiB₂-SiC coating. In contrast, a Zr-Ti-Si-O multiphase oxide layer with some micropores, comprising embedded ZrTiO₄ and ZrO₂ phases and a semi-continuous SiO₂ glass phase, develops on the ablative surface of ZrTiB₂-SiC coating. High-melting-point phases, such as HfTiO₄, HfO₂, ZrTiO₄, and ZrO₂, effectively counteract high-temperature flame erosion. Meanwhile, TiO₂ and SiO₂, possessing high-temperature fluidity, can seal the pore defects generated by erosion and thereby preventing oxygen from diffusing into the coatings and substrates. Therefore, the synergy between high-temperature skeletons and filling phases significantly enhances the anti-ablation protection of coatings.