The invention relates to a high-resistance ground fault line selection method for a small-current grounding system. According to the method, a plurality of feeder terminals arranged on each of all monitoring points of a line collect the zero-sequence current and the zero-sequence voltage of each monitoring point in real time. When the collected amplitude of the zero-sequence voltage of a bus is within a threshold section, the occurrence of a high-impedance grounding fault is detected and the fault location is further conducted. According to a fault line selection result, the transient-state zero-sequence current at each monitoring point on the upstream or downstream of each section of the fault line is projected onto the transient-state zero-sequence voltage of the bus, and then projection coefficients calculated. After that, the projection coefficients of the projectional components of all the transient-state zero-sequence currents at each of all monitoring points are compared, and the downstream section of a monitoring point with a largest projection coefficient is adopted as a fault section. According to the technical scheme of the invention, the fault location problem of the high-impedance grounding fault of the small-current grounding system is solved. Meanwhile, a location method based on the comparison of the projection coefficients of the projectional components of all the transient-state zero-sequence currents at each of all monitoring points on the upstream or downstream of each section of the fault line is provided. Therefore, the method has a wide practical application value.