<p>In order to investigate the effects of oxide particles on the high-temperature resistance and ablation performance of ceramicizable phenolic resin composites, three types of quartz fiber-reinforced ceramicizable phenolic resin composites were prepared using MgO particles or Al₂O₃ particles as the second-phase oxides and ZrB₂ particles as the high-temperature ceramic filler, through a mold pressing process. The enhancement effects and mechanisms of the added second-phase oxides on the high-temperature resistance and ablation performance of the composites were discussed and analyzed through high-temperature testing, phase characterization, oxyacetylene testing, and microstructure characterization. The results show that ZrB₂ particles oxidize to form ZrO₂ and B₂O₃ in an oxygen-rich high-temperature environment. The added second-phase oxide particles can react with B₂O₃ to form corresponding borates, thereby strengthening the matrix. After treatment at 800 °C, the flexural strength of the ZrB₂-MgO quartz fiber-reinforced phenolic resin composite (QFPR/ZM) increased by 55.3% compared to the ZrB₂ quartz fiber-reinforced phenolic resin composite (QFPR/Z). The oxyacetylene ablation performance of the composites with added oxide particles was significantly influenced by the generated borates. Mg₃B₂O₆ has a higher high-temperature viscosity than Al₁₈B₄O₃₃ at high temperatures, resulting in a lower linear ablation rate for QFPR/ZM compared to the ZrB₂-Al₂O₃ quartz fiber-reinforced phenolic resin composite (QFPR/ZA).</p>