The invention provides a power distribution automation system's single-phase grounding section precisely positioning method, comprising the following steps: 1) when the single-phase grounding occurs in a power distribution network, using the fault phase identification algorithm to recognize the phase with grounding fault and letting the phase with grounding fault grounded for a short time before having it ungrounded; 2) measuring the zero sequence current detected at the terminals of each outlet line that are nearest to the transformer station by the power distribution automation main station; and determining that the outlet line whose zero sequence current is reduced obviously in contrast to the prior short time grounding is the line with single-phase grounding fault; and 3) when the line with fault is determined, measuring the monitored components of all terminals along the line with fault by the power distribution automation main station; comparing the conditions before short time grounding and after short time grounding for the downstream of the last stage in which the zero-sequence current direction does not change; and determining that the section between the terminals showing no obvious change in the zero-sequence current before the short time grounding and after the short time grounding is the single phase grounding section. According to the invention, through short time grounding, it is possible to obviously change the distribution of zero sequence current across the line with fault and a fault area. Therefore, the single phase grounding section in power distribution automation can be recognized more accurately.