Abstract: The paper analyzed advantages and disadvantages of line selection methods for small current grounding of coal mine high-voltage power grid that are relatively mature in both theoretical research and application.Based on accuracy of line selection,no malfunction,a wide range of adaptability to different fault types and adaptability to neutral isolated or petersen-coil grounding modes,it proposed a complementary comprehensive selection method which combined steady-state and transient-state selection methods,and gave the block diagram of principle of the method.