We propose a novel preparation technology of CNTs modified electrode. CNTs are mixed with polymer into homogenate by mechanical ball grinder; spin homogenate into composite film; solidify and polish composite film; chemical etch polymer partly from the surface of the composite film, in order to keep part of the CNTs be inserted in polyimide and the remainder outside of film, then CNTs modified electrode can be got. The morphologies of CNTs modified electrode are observed by field emission scanning electron microscopy (FESEM). The application of CNTs modified electrode in alum solution battery is demonstrated. Cyclic voltammetry of CNTs modified electrodes in V4+ solution is discussed.