The capacitance of an electrolytic capacitor depends on the impedance presented when it operates at an alternating current voltage. Therefore, the capacitance value, that is, the AC capacitance value, varies with the change of working frequency, voltage and measurement method. The standard JISC 5102 stipulates that the measurement conditions of the capacitance of aluminium electrolytic capacitors are: the frequency is 120 Hz, the maximum AC voltage is 0.5 Vrms, and the DC bias voltage is 1.5-2.0 V. It can be concluded that the capacitance of aluminium electrolytic capacitors decreases with the increase of frequency.