High quality silicon carbide single crystal nanorods were successfully synthesized through gas-solid reaction between silicon and multiwall carbon nanotubes (CNTS) by direct heating methods. The X-ray diffraction (XRD) analysis showed that the reaction product of Si vapor with CNTS is beta-SiC. SEM and HRTEM images suggested that the SiC nanorods are 3C-SiC single crystals almost free of defects. Based on these results, it is presumed that the reaction first took place at an end of CNTS giving beta-SiC nuclei, one of which with its [111] parallel to the tube direction could grow consecutively along this direction so that a straight and solid SiC single crystal rod was formed without defects.