Abstract: The paper introduces the principle of small current grounding line selection and clarifies its advantages and disadvantages. It analyzes the reasons for inaccurate line selection in small current grounding, which are mainly affected by the hardware of the line selection device and the zero sequence circuit. In response to the above problems, governance requirements are proposed, which can effectively improve the accuracy of line selection. Finally, through reasoning and analysis of typical grounding fault waveforms, it can provide certain guidance and reference for relevant personnel on site.