This paper calculates respectively energy of every band in zero sequence current of every line with frequency decomposition and signal reconstruction to select the band with the maximal energy as the feature band. At first, it selects all the “likely faulty” lines by comparing the maximal magnitude zero current and the corresponding polarity in all lines and the polarity of the zero sequence voltage’s first half wave, and then, by detecting maximum value of the second break point at the instant of the medium resistance is launched to select the fault line. Simulations indicate that this way is correct and effective.