The invention discloses a distribution line single-phase earth fault positioning method, and belongs to the technical field of distribution automation. The method is characterized by comprising the following steps of: a, continuously sampling and recording the current value and voltage value of a point; b, if the amplitude break variable of the voltage value or the current value is greater than orequal to a preset value, executing the step C, otherwise, returning the step a; c, storing the data before and after the fault point; d, carrying out calculation to obtain a fault distance; and f, obtaining a fault distance curve and obtaining a final fault distance according to the fault distance curve. According to the distribution line single-phase earth fault positioning method, calculation is carried out by utilizing an inductance relationship between the line outlet and the fault point so as to obtain the fault distance; the fault judgement and calculation method constructed through a simplified line fault equivalent model is rapid in calculation and is capable of eliminating effects through planned maintenance before permanent faults occur, so as to nip in the bud, decrease the un-scheduled outage and improve the power supply reliability of the whole line.