The present invention discloses an identification method of a power distribution network single-phase earth fault phase. The method comprises obtaining operation parameters of a system in real time; calculating a locus curve of zero-sequence voltage changed with transition resistance when A, B and C phases have single-phase earth faults in the same coordinate system; when the single-phase earth fault happens, detecting a fault zero-sequence voltage vector, and drawing the fault zero-sequence voltage vector in the same coordinate system; and determining the fault phase of the single-phase earth fault according to the relative position of the position of the terminal point of the fault zero-sequence voltage vector and the locus curve of the zero-sequence voltage changed with transition resistance when A, B and C phases have single-phase earth faults. The identification method of the power distribution network single-phase earth fault phase accurately calculates the zero-sequence voltage locus prior to the failure occurrence, can effectively realize identification of the single-phase earth fault phase, is suitable for the small-current grounding system of neutral points in various modes, especially can effectively solve the problem of the identification of the asymmetric system high resistance grounding fault, can overcome the limitation of a traditional phase selection method, and has good application prospects.