Abstract: For the problem that failure current was small of grounding point of neutral point grounding system grounded by arc suppression coil when single-phase ground fault occurs, the paper proposed a kind of current leakage protection method of coal mine based on time-sharing ratio of phase current amplitude. The method obtains summation ratio of mutual integral of transient current and steady-state phase current by sampling and calculation, and conducts leakage protection of transient current and steady-state phase current respectively, then makes judge conclusion according to the larger phase current ratio, so as to automatically select the fault line and trip. The Matlab simulation results show that the method can effectively achieve leakage protection, and the line selection results are accurate and reliable.