The invention discloses a preparation method of a large rod bank beam-shaped nano cerium dioxide and activated carbon composite electrode material for a super capacitor. The method comprises the steps of: adding CeCl3.7H2O and urea to water for stirring evenly, putting the mixture into a reaction kettle for a temperature rise, carrying out a hydrothermal reaction, washing the obtained white sediment and then burning the white sediment in a muffle furnace to obtain large rod bank beam-shaped nano cerium dioxide; and preparing a rod bank beam-shaped nano cerium dioxide/activated carbon compound from activated carbon and the large rod bank beam-shaped nano cerium dioxide, and then preparing the large rod bank beam-shaped nano cerium dioxide/activated carbon composite electrode material from the rod bank beam-shaped nano cerium dioxide/activated carbon compound, a conductive agent acetylene black and a binder. The preparation method has the advantages that the preparation method is simple, the specific capacitance is high, the charge transfer resistance is small and the large rod bank beam-shaped nano cerium dioxide and activated carbon composite electrode material is suitable for being used as an electrode of the super capacitor.