Abstract: Due to the influence of power system structure, operating conditions and other factors, the existing route selection methods have some shortcomings. In order to ensure the accuracy of line selection, this paper presents a method of line selection with pulse current, which flows through the fault line and combines with the second harmonic component detection technology to detect. The model and simulation of the non-effective grounding system with neutral point are carried out, and the field test of the high voltage laboratory is carried out to verify the effectiveness of the method.