The embodiment of the invention provides a method and device for measuring the impact grounding resistance, relates to the technical field of thunder protection, and solves a problem that the measured impact grounding resistance cannot be used as reference because the difference of the whole current loop impedance will cause the difference of an outputted current waveform in the prior art. The method comprises the steps: injecting a constant amplitude current input signal with the frequency being swept to the highest frequency from the fundamental frequency of a thunder current to a grounding body; measuring the voltage response sequence and an outputted current response sequence of the grounding body at different frequencies; carrying out the correction of the outputted current response sequence, obtaining a first current response sequence with the constant amplitude, correcting the measured voltage response sequence according to the outputted current response sequence and the first current response sequence with the constant amplitude, and obtaining a first voltage response sequence; and determining the impact grounding resistance of the grounding body according to the first current response sequence with the constant amplitude, the first voltage response sequence and a thunder current waveform spectrum expanded sequence.