The invention belongs to the technical field of the processing of single-phase earth faults of a power system, and relates to a single-phase earth fault line selection method for a small current grounding system. The method comprises the steps: 1), carrying out the statistics of historical fault data of the same bus; 2), extracting a historical grounding line set of the same bus; 3), determining the historical fault measure of a grounding line at different scales; 4), carrying out the weighted fusion of the historical fault measure of the grounding line; 5), carrying out the selection of a pull line according to comprehensive grounding probability; 6), updating the historical fault data of the same bus. The method irons out the defects that a conventional line selection method is high in misjudgment rate because the electrical quantity is affected by a power grid operation mode and equipment parameters during a fault, improves the selection accuracy and efficiency of the single-phase earth pull line, reduces the number of selection times of the pull line, and guarantees that a power distribution network supplies power for a user safely and reliably.