A carbon micro-sensor electrode is disclosed which is prepared by impregnating, adsorbing or chemically modifying a pure composite carbon wire having many micropores extending to its surface and interior with a reactant such as an enzyme, a metal complex compound, an organic compound or a metabolite; and a method for preparing this carbon micro-sensor electrode is also disclosed.The above-mentioned electrode can be used for a long period of time, since the reactant is received in the many micropores. Furthermore, after used, the electrode may be cut off to expose a new electrode surface, and this new electrode surface may be coated with a material which does not impede an electrode reaction, whereby the reactant can be prevented from flowing out. Thus, the carbon micro-sensor electrode of the present invention can be repeatedly utilized.