The invention relates to an aluminum electrolytic capacitor, the anode of which has an oxidation voltage of not greater than 30V. The aluminum electrolytic capacitor comprises a dispersion that includes a conductive polymer and a dispersant. The average particle diameter of the conductive polymer is 5-40nm. The invention also relates to a method for preparing the aluminum electrolytic capacitor. The aluminum electrolytic capacitor of the invention has the advantages of easy capacitance generation, low loss, low equivalent series resistance and low electric leakage.