A method for preparing an electrolytic copper foil includes placing an anode and a cathode to be plated in a twin crystal growth agent containing electroplating solution in an electroplating tank, and, under conditions that the electroplating solution is provided with randomly alternating transitions of one or two of an ultrasonic wave at a frequency f11 and an ultrasonic wave at a frequency f12 and one or two of an ultrasonic wave at a frequency f21 and an ultrasonic wave at a frequency f22, performing direct current electroplating to obtain the electrolytic copper foil, wherein f11>40 kHz, 15 kHz