The invention discloses a high-resistance grounding fault positioning method based on transient current projection coefficient difference comparison, which is characterized in that when a system has a high-resistance grounding fault, a substation terminal starts, a fault line is selected, and a line selection result and fault line outlet zero-sequence current acquisition data are reported to a master station; when a sudden change of zero-mode voltage or zero-mode current exceeds a preset threshold, each feed line terminal starts, and fault zero-sequence voltage and current acquisition data is reported to the master station; the master station receives zero-sequence voltage and current acquisition data of each monitoring point of the substation terminal and feed lines, respectively extracts transient components thereof and does not perform processing on sound line terminal data; projecting the transient zero-sequence current of each monitoring point to transient zero-sequence voltage of a bus, and calculating a projection coefficient of the transient zero-sequence current of each monitoring point; calculating the difference of the transient zero-sequence current projection coefficients of upstream and downstream monitoring points of each segment; and selecting a segment with the greatest difference to be a fault segment. The high-resistance grounding fault positioning method solves a problem of positioning a high-resistance grounding fault in a resonant grounding system and has wide practical application values.