In order to improve the reliability of lineselection and faultlocation for singlephase grounding failures in distribution network, the current waveform at different stages were studied and stimulated. Firstly, in terms of the summarized common features of current waveforms during their development, the incremental current of the subtransient sawtooth wave in the grounding phase and the incremental current in the sound phase are selected as the criterion signal sources for the fault location of the insulation loss in distribution networks. The general characteristics of all grounding currents reflected by the saw tooth currents are analyzed. Then, the difference of waveform characteristics is analyzed between singlephase grounding current and operationinduced disturbance currents. It provides a criterion for identifying the authenticity of singlephase grounding failure. The line selection and location method are proposed for the singlephase grounding including the insulation loss to avoid misidentification. Finally, the proposed method is applied to the grounding locator in a low voltage distribution network model for verification.