The invention provides an annular carbon electrode and a method for preparing a Co nanowire/ alumina film from the same. The annular carbon electrode comprises a carbon plate and a non-conductive film covering the carbon plate, wherein an annular exposed area is formed on the carbon plate. A preparation method of the annular carbon electrode comprises following steps: the size and the position of the annular exposed area are determined on the carbon plate; the carbon plate outside the annular exposed area is covered with the non-conductive film, and the annular carbon electrode is obtained. The annular carbon electrode is simple to prepare and is practical, all that is required is to apply an alternating current deposition process once to prepare the Co nanowire/alumina film, and the prepared Co nanowire/alumina film has gradually varied magnetism and can show highly-saturated annular irisation structural color.