We have developed a novel synthesis method for single-walled carbon nanotubes(SWNTs) which are expected to be the core material for nanotechnologies. This method modified from the direct injection pyrolytic synthesis method has dramatically achieved high purity and a high degree of graphitization by controlling the reaction conditions accurately. The purity of the nanotubes increased from 50% to 97.5% and the structural defects in the nanotubes were reduced to one tenth of the previous level. Without purification processes, surface treatments or binders, these high quality SWNTs can be used to make high-strength threads (SWNT wire) and SWNT mesh sheets.