Controlling the structure and properties of low-density C/C porous preforms is the key to the preparation of C/C-SiC composites with excellent friction and wear properties. In this study, C/C porous preforms prepared by chemical vapor infiltration were subjected to high temperature heat-treatment at 2100 ℃. C/C-SiC composites were prepared by reactive melt infiltration. Effects of high temperature heat-treatment of C/C porous preforms on microstructures, thermal properties and tribological properties of C/C-SiC composites were investigated. The results showed that the porosity and graphitization degree of the C/C porous performs increased after high temperature heat-treatment at 2100 ℃. The C/C-SiC composites have a higher density (2.22 g/cm³), and the porosity is reduced from 5.1% to 3.4%, the phase content of SiC ceramic is increased by 11.9%. The mean free path of phonons is larger when C/C porous preforms have a higher degree of graphitization, resulting in thermal conductivity at room temperature being increased by 2.1 times, and the thermal conductivity at 1200 ℃ being increased by 0.2 times. Wear surface of C/C-SiC composites forms a continuous and stable friction film, which is attributed to the fact that the PyC after high temperature treatment is softer and easier to be extruded into a film. Thus, the friction coefficient is more stable, and the wear rate is reduced under the test loads of 3, 6 and 9 N, by 47.8%, 41.9% and 11.7%, and the average friction coefficients are 0.47, 0.38 and 0.39, respectively. Therefore, high temperature heat-treatment of the C/C porous preforms can improve the thermal conductivity of the C/C-SiC composites, which exhibits a more stable friction coefficient and more wear-resistant.