Vertically-aligned carbon nanotubes (CNTs) were prepared by hydrogen arc discharge, using pure graphite powder as carbon source without catalysts added. Scanning and transmission electron microscopy characterizations show that the aligned CNTs have a bamboo-like structure, and their lengths and diameters are about 30 μm and 40–60 nm, respectively. No metallic impurities can be detected in the samples by careful X-ray photoelectron spectroscopy detection. The activation of hydrogen radicals, the heating effect of the arc, and the electric field surrounding the arc column area are considered to play important roles for the non-catalyst growth of the CNTs.