There are shortcomings in the existing distribution network automation equipment and methods, in that they find it difficult to quickly and accurately detect single-phase grounding fault of lines. Thus a single-phase grounding fault detection method for a distribution network based on phase voltage difference polarity value is proposed. By analyzing the voltage amplitude characteristics of the single-phase ground fault for a neutral point ungrounding system and the neutral point through the arc suppression coil grounding system, the voltage amplitude relationship between the fault phase and the non-fault phase is obtained. From the voltage amplitude law of fault phase and non-fault phase, the voltage difference polarity valueis defined. The corresponding single-phase grounding fault detection criterion is established to realize the rapid detection of a single-phase grounding fault of the line. Simulation results show that the proposed method can effectively detect the single-phase grounding fault of the line, and the detection results are not affected by the neutral point grounding mode, load fluctuation and fault angle. It also has good resistance to high-impedance faults. Field tests show that the proposed method can detect single-phase grounding faults within 3 ms, and can effectively detect the single-phase grounding fault with a 2.5 k resistance. This has good engineering applicability.