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 C/C composite of 1.28 g•cm-3 was densified to C/C-ZrC-SiC composite of 1.42 g•cm-3 after infiltration and pyrolysis once, the density increased 10.94%. The linear ablation rate and mass ablation rate of the C/C-ZrC-SiC composites (ρ=1.42g•cm-3) were 7.22μm•s-1and 3.88mg•s-1, which decreased 79.31% and 65.46% comparing with C/C composite of 1.28 g•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.