In view of the high-voltage power grid in coal mine, the neutral point is not grounded or grounded through the arc suppression coil. When a single-phase ground fault occurs, the fault current is very small and it is difficult to identify, which leads to the problem of misoperation and rejection of the comprehensive protection device based on the traditional power frequency steady-state line selection theory. This paper analyzes the transient electrical characteristics of the instantaneous ground fault, and points out that the compensation effect of the arc suppression coil is the root cause of the failure of the traditional protection. A fault identification and hierarchical early warning method based on zero-sequence current transient signal capture is proposed, and a technical scheme combining high-frequency signal acquisition, time-frequency feature extraction and bus difference comparison algorithm is designed. Through the field comparative test in Yulin Coal Mine of Shaanxi Province and the practical application in Handan, Xingtai and other coal mines of Hebei Province, the superiority of the proposed method in fault identification accuracy, response speed and early warning ability is verified, which effectively solves the problem of early warning and accurate line selection of ground fault in high voltage power grid underground coal mine.