Abstract: An electronic device and a detection method of power capacity are provided. The electronic device includes a battery and a power management unit coupled to the battery. The power management unit reads an output voltage of the battery, and determines whether a variation of the output voltage of the battery within a time interval is greater than a threshold. When the power management unit determines that the variation of the output voltage of the battery within the time interval is greater than the threshold, the power management unit calculates a remaining power capacity of the battery according to the output voltage and the variation of the output voltage within the time interval.