The invention relates to the technical field of distribution network relay protection, and more particularly relates to a single-phase ground fault detection method for a neutral point small resistance grounding distribution network. The method is based on the significant difference between the faulty line and the non-faulty line of the ratio of the zero sequence current integral value to the zerosequence voltage difference, and determines whether the single-phase ground fault occurs through the ratio average value of the line. The ratio average value of the non-faulty line is approximately equal to 106 times the capacitance value of the line to the ground. Since the grounding small resistance exists only in the zero-sequence equivalent network through which the zero-sequence current flows through the faulty line, the ratio average value of the faulty line is larger than that of the non-faulty line, and it is possible to effectively determine whether a single-phase ground fault occurson the line. The method is less affected by the transition resistance, and can improve the sensitivity of the protection to the high-resistance ground fault, thereby improving the safety and stability of the distribution network and reducing the probability of a safety accident caused by the high-resistance ground fault.