Abstract: The phenomenon of harmonic wave and arc light in mine power grid is increasingly serious, and leakage fault signal distortion and probability of arc light leakage increases, resulting in serious fault signal distortion and less fundamental wave component. However, the existing leakage protection methods of mine power grid adopt zero-sequence fundamental wave component as fault characteristic parameter, which has a low identification rate for arc light leakage. In view of the above problems, an intelligent leakage protection method of mine power grid based on equivalent conductance was proposed. On the basis of analyzing characteristics of leakage fault, the zero-sequence current is decomposed orthogonally with distorted zero-sequence voltage as reference according to non-sinusoidal power theory. The distortion equivalent conductance is adopted as fault characteristic parameter, and the leakage circuit is identified by comparing symbols and value of equivalent conductance of each feeder: the circuit with the maximum equivalent conductance and negative sign is judged to be leakage branch, and alarm and tripping command are issued; the equivalent conductance with a positive symbol represents current insulation level of corresponding non-leakage feeders to realize automatic monitoring of cable insulation state. The orthogonal reactive current is adopted to reflect capacitive current level of the grid, which provides data support for mine power supply safety analysis and fault warning. Simulation results show that the method can realize leakage fault identification, leakage branch location and automatic monitoring of cable insulation state, and meets requirements of selectivity, rapidity and sensitivity, especially suitable for arc leakage fault identification, which can effectively improve safety of the mine power supply.