The present application provides a method for harmonic impedance scanning of a high-voltage direct current transmission system, which comprises the following steps: harmonic current with a starting frequency and an initial amplitude is injected into the system; after the system enters into a steady state, the response value of the harmonic voltage and the harmonic current of the measuring point are extracted; the amplitude of the harmonic current is gradually increased until the amplitude of the harmonic current reaches the upper limit of the amplitude, and the harmonic impedance value under the said starting frequency is calculated according to the measuring result after each increasing of amplitude value; the frequency of the harmonic current is gradually changed according to the presetfrequency step until reaching the cut-off frequency, and the harmonic impedance value at other frequencies is continued to be measured according to the above-mentioned steps. Eliminating the interference of the disturbance amplitude on the measuring result in the system, the harmonic impedance of the high-voltage direct current transmission system is accurately measured.