A direct current (DC) fault arc detection method, including performing sampling, filtering and fast Fourier transform (FFT) on an input current of a high frequency power electronics converter, to obtain an amplitude-frequency characteristic curve of a current high frequency component; and selecting, from the amplitude-frequency characteristic curve, at least one frequency band including a switching frequency or a multiple frequency, calculating a peak value D1 of amplitudes and an average value D2 of the amplitudes within the frequency band, and determining, according to a change of a distance between the peak value D1 and the average value D2, whether an arc occurs, where if the average value D2 approaches the peak value D1, an arc occurs; otherwise, no arc occurs.