The SiC/SiC with dispersed carbon nano-fibers (CNFs) composites were fabricated in order to improve the thermal conductivity. The SiC/SiC with and without dispersed CNFs composites were fabricated by reaction bonding (RB) process. The effect of dispersed CNFs on the thermal properties was investigated The volume fraction of CNFs was approximately 4 %. The CNFs were successfully dispersed in the SiC/SiC composites without reducing the volume fraction of SiC fibers. It is, therefore, considered that the strength of SiC/SiC with dispersed CNFs composites is not reduced. The thermal conductivities of the composites were measured in the temperature range from room temperature to 1000°C. The thermal conductivities of SiC/SiC with dispersed CNFs composites were twice as high as those without CNFs; the value was approximately 90 W/mK at room temperature. The thermal conductivity of SiC/SiC with dispersed CNFs composites at 800 °C, which is the operation temperature range of fusion reactors, was more than 40 W/mK. The thermal conductivities of SiC/SiC with dispersed CNFs composites in this study satisfy completely the assumed design criterion for fusion reactors, which is 15-20 W/mK at the operation temperature of fusion reactors.