Abstract: Coaxial nanocables of single-walled carbon nanotubes (SWCNTs) sheathed with amorphous silicon oxide were directly synthesized by a hydrogen arc discharge method. As-prepared nanocables are usually tens of microns in length and about 10-30nm in diameter. The sheath of the nanocables is amorphous silicon oxide, while the core is high quality SWCNTs. Each cylinder-shaped nanocable contained one to several SWCNTs. The growth mechanism of the nanocables is proposed. These SWCNT/amorphous silicon oxide nanocables may have potential applications in field effect transistors and other related nanodevices.