It was reported that carbon nanotube (CNT) was functionalized with the electroactive Nile blue (NB), which is a phenoxazine dye, by a method of adsorption to form a NB-CNT nanocomposite. The NB-CNT nanocomposite was characterized by several spectroscopic techniques, for example, Ultraviolet-visible spectroscopy (UV-VIS), Fourier transform infrared (FTIR), Raman spectroscopy and scanning electron microscopy (SEM) etc., and the results showed that NB could rapidly and effectively be adsorbed on the surface of CNT with a high stability without changing the native structure of NB and the structure properties of CNT. More-over, it was shown that the dispersion ability of CNT in aqueous solution had a significantly improvement after CNT functionalized with NB even at a level of high concentration,for example, 5 mg of NB-CNT per 1 mL of H20. The NB-CNT/glasssy carbon (GC) electrode was fabricated by modifying NB-CNT nanocomposite on the GC electrodesurface and its electrochemical properties were investigated by cyclic voltammetry. The cyclic voltammetric results indi-cate that CNT can improve the electrochemical behavior of NB and greatly enhance its redox peak currents. While the NB-CNT/GC electrode exhibited a pair of well-defined and nearly symmetrical redox peaks with the formal potential of (-0.422±0.002) V (versus SCE, 0.1 mol/L PBS, pH 7.0),which was almost independent on the scan rates, for electrochemical reaction of NB monomer; and the redox peak potential of NB polymer located at about -0.191 V. The experimental results also demonstrated that NB and CNT could synergistically catalyze the electrochemically oxida-tion of NADH (β-nicotinamide adenine dinucleotide, reduced form) and NB-CNT exhibited a high performance with lowing the overpotential of more than 560 inV. The NB-CNT/Gcelectrode could effectively sense the concentration of NADH,which was produced during the process of oxidation ofsubstrate (e.g. Ethanol) catalyzed by dehydrogenase (e.g.alcohol dehydrogenase). The presented method for function-alization of CNT had several advantages, such as rapid and facile CNT functionalization, easy electrode fabrication and high electrocatalytic activity, etc., and could be used for fabrication electrochemical biosensor on the basis of dehydrogenase.