The ablation properties of C/C-ZrC-SiC composites prepared by precursor infiltration and pyrolysis processes were studied by the H2-O2 ablation method. The results indicate that the ablation rate of C/C-ZrC-SiC composites decreases with increasing density of the composites. The linear ablation rate and mass ablation rate of the C/C-ZrC-SiC composites (ρ=1.69g·cm-3) were 0.00211mm·s-1 and 0.5179mg·s-1, only 20.6% and 31.6% of those of C/C composites (ρ=1.78g·cm-3) respectively. The introduction of ZrC-SiC into the matrix greatly enhanced the anti-oxidative and ablation property of the C/C composite. The ablation mechanisms of the C/C-ZrC-SiC composites were supposed to be the synergistic effects of thermo-chemistry ablation (oxidation and sublimation) and mechanical erosion.