Abstract: C/C preforms were prepared by densification of carbon fiber felts, using furan resin impregnation, carbonization, CVD and an initial high temperature treatment (HTT) at 2000-2400℃ followed by a second resin impregnation and carbonization. The C/C-SiC composites were manufactured by molten silicon infiltration of the as-obtained C/C preforms at 1650℃ with or without a second HTT. The effect of the first HTT on the density, porosity, mechanical properties and fracture mode of the C/C-SiC composites was studied. Results show that the first HTT results in C/C-SiC composites with a “pesuo-plastic” fracture mode and better general mechanical properties. The second HTT of the C/C preforms results in carbon with open porosity, which is favorable for molten silicon infiltration, leading to a C/C-SiC composite with high density and low porosity, but the mechanical properties decrease while the fracture mode is unchanged.