Transient electrical quantity information is very abundant when single-phase grounding fault occurs in resonant earthed system. The short window data of 1/4 period of zero sequence current fault of each line are transformed by wavelet transform. The frequency band of power frequency is eliminated and the feature frequency band is selected according to the principle of maximum energy sum. The reconstructed wavelet coefficients under the feature frequency band are checked by morphological peak-valley detection. The peak-valley characteristic of the fault feeder is opposite to that of the total feeders

which is used as the fault line selection criterion. The simulation analysis and practical verification demonstrate the feasibility and effectivity of this method.