Provided is an adaptive impedance protection method for parallel capacitors, the method comprising monitoring terminal voltage and current of a capacitor; automatically calibrating, when the capacitor is put into operation, the initial impedance of the capacitor; during operation, calculating the real-time impedance of the capacitor and dynamically and periodically updating the real impedance of the capacitor; by comparing the real-time impedance and real impedance of the capacitor, if a relative value of a modulus of the variation of the real-time impedance does not exceed a dynamic update limitation threshold and reaches an update period, updating the real impedance, and if same exceeds the dynamic update limitation threshold, giving an update failure warning; if the relative value of the modulus of the variation of the real-time impedance exceeds a set protective warning threshold and a delay time arrives, giving out a fault warning; and if the relative value of the modulus of the variation of the real-time impedance exceeds a set protective trip threshold and a delay time arrives, protecting a trip exit. The protection method is applicable to various faults of a capacitor and a capacitor bank, is simple in calculation of a setting value, is simple and convenient to implement, and effectively improves the sensitivity and reliability of capacitor protection.