Carbon nanotube (CNT) is a kind of inorganic material with a nano-struclurc. The subtle electronic properties suggest that carbon nanotubes have the ability to promote electron transfer reaction when used as an electrode. They have been used as modified electrodes to catalyze the electrochemical reaction of some molecules and bio—molecules, such as dopamine, NADH, cytochrome c, etc.[1-2J. In the present study the electrochemical behavior of thionin incorporated on multi-wall carbon nanotubes (MWNTs) modified OC eJectrode is investigated by cyclic voltametry (CV) and choronoarnperometry.