This study focuses on the conditions of preparation of C/C-SiC composites through polymer infiltration and pyrolysis method using hydrogen-containing polysiloxane as the precursor and divinylbenzene as cross-linking agent. The densities of different C/C composites (ρ=1.02, 1.21, 1.60, 1.78g·cm-3) increased to 1.24, 1.36, 1.69, 1.84g·cm-3 respectively after infiltration and pyrolysis four times. The appropriate ratio of hydrogen-containing polysiloxane and divinylbenzene was 1/0.5. The appropriate cross-linking temperature was 250°C. In pyrolysis process, the appropriate increasing rate of pyrolysis temperature should be 50°C/h in the range of 300-800°C. SiC was formed when pyrolysis temperature reached 1550°C.The linear ablation rate and mass ablation rate of C/C-SiC composites were much lower than those of C/C composites.