In this paper, we have successfully synthesized polyaniline nanotubes by using chemical oxidation polymerization. This synthesis is simple and an effective way to prepare one-dimensional polymer nanotubes. By transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FTIR), the morphology and physical structures of the as-prepared products were characterized. By cyclic voltammetry we studied the electrocatalytic activity of polyaniline nanotube modified glassy carbon electrode on ascorbic acid. The results show that the polyaniline nanotube modified electrode has excellent electrocatalytic activity on ascorbic acid. Compared with those of the bare glassy carbon electrode, the anodic peak potential of ascorbic acid shifts negatively 0.212 V on the modified electrode, and the anodic peak current increases 43 %. And the concentration of ascorbic acid shows a good linear relation at the range of 1.0×10-5 ~ 0.1 M with the minimum detection limit of 1.0 × 10-6 M.