The C/C-SiC composites are prepared by the reaction molten infiltration process of silicon powders, using porous C/C composites as preform. C/C composite frameworks with various bulk densities are prepared by the chemical vapor infiltration (CVI) combined with the resin impregnation-pyrolysis methods, using needled-carbon fiber felts as preform. Characterization of the microstructure was conducted with a digital microscope (VHX-500) and a polarized light microscopy, respectively. The hardness (H) and the elastic modulus (E) of the composites are measured using a nano indentor. The results show that the indentation behaviors of the pyrolytic carbon and resin carbon are elastic while silicon and silicon carbide show a plastic deformation behavior. The hardness of the resin carbon as well as the pyrolytic carbon is 2.1GPa and 1.3~1.6GPa, respectively. E of SiC varied from 360 to 259GPa and H from 36 to 21GPa. For Si, the value of E and H are 155-170GPa and 11.7GPa, respectively. The relationship between microstructure and mechanical properties of C/C-SiC composites were analyzed.