The invention discloses a preprocessing method for increasing hole generation density of an electrode foil used by an aluminum electrolytic capacitor. The method comprises the following steps of preprocessing, first washing, hole generation processing, neutralization processing, secondary washing, hole reaming processing, third washing, chemical cleaning, fourth washing and drying. In the invention, through improving a preprocessing condition, uniformity of aluminum foil surface corrosion pit distribution is increased, a thickness reduction amount of an aluminum foil is reduced, and finally the electrode foil used by a middle and high voltage aluminum electrolytic capacitor is acquired, wherein hole distribution is uniform, hole lengths are consistent, and residual core layer thickness isuniform in the electrode foil. After formation, a capacity and intensity are greatly increased.