When a single-phase and high-resistance ground fault occurs in the low-resistance ground system, the feeder zero-sequence current is lower than that of the traditional time limit zero-sequence over current protection fixed value, leading to the problem of protection. This paper proposes a high-resistance ground fault protection method based on zero-sequence admittance in low-resistance ground system. Firstly, the electrical quantitative characteristics are analyzed when the single-phase ground fault of the low-resistance ground system occurs. Through the theoretical derivation, it is found that the zero-sequence admittances of the fault line and non fault line are not related to the transition resistance and fault position, but only to the system zero-sequence resistance and operation mode. And for the fault line and non fault line, there is a significant difference in theirs zero-preparation admittance angles. Furthermore, through quantitative calculations, the fault area and non-fault area are divided in the admittance compound plane. The results show that the tolerance transition resistance capacity of proposed method is above 1.4 kΩ.