The large-scale synthesis of high-purity SiC nanowires is a challenge. In this context, sponge-like graphene oxide (GO) was used as a carbon source as well as a reaction template for directly synthesizing SiC nanowires. GO was completely reacted with SiO to prepare high-purity 3C-SiC nanowires by thermal evaporation and carbothermal reduction without the use of any catalyst, rather than by epitaxy. Characterization was conducted using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected-area electron diffraction. The SiC nanowires had lengths of several tens of micrometers and a perfect single-crystalline structure with a bamboo-like morphology.