In order to accurately detect single-phase ground fault in resonant grounding systems, a fault line selection method based on fault transient amplitude measure is proposed. With the modulus transform, feeder fault and normal feeder after fault are analyzed. By using wavelet modulus maxima characteristic current, the law of zero mode initial current wavelet modulus maxima is developed. The transient amplitude fault measures are defined combined with this law and the general fault measures. The transient amplitude fault measure of the fault feeder is maximum, and the normal ones is greater than 0 and close to 0. Accordingly, the fault line selection method is proposed and the fault feeder is detected. Theoretical analysis and ATP simulation results show that, this method can effectively detect single-phase ground fault in resonant grounding systems, and is not influenced by arc suppression coil.