A reliable and practical identification and location method is needed for the frequent line-broken fault of a distribution network. In this paper, a fault model is established for the single-phase line-broken fault in a resonant grounded system. Factors that may affect the fault characteristics are considered, including an ungrounded fault, a disconnected fault or a power side or load side grounding fault, as well as disconnection position, load impedance, grounding resistance of the sinking point and the degree of compensation of the system. By combining theory with simulation analysis, a law of ground potential and neutral offset voltage is analyzed, and the variation characteristics of all phase voltage and line voltage before and after fracture are obtained. The results show that, different from the simple earth fault, the ground potential distribution range is larger, and the line voltage before and after the fracture is obviously different from the three-phase voltage. The conclusions can provide a theoretical basis for research on fault detection and location on a distribution network with voltage signal. This work is supported by the National Natural Science Foundation of China (No. 52077221) and the Research and Application on Key Technologies of Promoting Medium Voltage Distribution Network Single-phase Fault Treatment Efficiency of Kaili Power Supply Bureau in 2020 (No. 060800KK52190010).