Single-walled carbon nanotubes (SWNTs) possess outstanding electrical properties, which make them attractive building blocks for future electronics. The electrical properties of SWNTs are intimately related to their structural uniformity. Here, we reported well-aligned SWNTs, up to centimeter long, synthesized in an ultralow gas flow chemical vapor deposition (CVD) system using ethanol as the carbon source. The as-grown SWNTs were characterized using Raman spectroscopy and confocal Raman imaging. The low intensity ratio of D band and G band (ID/IG), together with the constant G band position over several millimeter length of an isolated SWNT, indicates that the structures of the individual SWNTs are uniform with exceedingly low density of defects. Excellent electrical performances were also observed by fabricating the as-grown SWNTs into FETs. The superior length and the well-ordered orientation, allow large scale fabrication of individual CNT-based electronic devices, and also show a promising prospect of creating integrated circuits on an individual SWNT.