The method of multi-zero sequence current transformer structure and compensation parameters is used to study the single-phase ground fault line selection of a small current grounding system. This paper designs the topology of the system, and analyzes the influence rule of the different sequence of compensation parameters on current amplitude and phase of each zero sequence current transformer and the problem of the sensitivity of fault line selection. The variation rule of the zero-sequence current flowing through the fault point and the safety problem of the fault current under different compensation parameters are analyzed. The line selection criterion of the line selection method has high reliability and adaptability, can accurately identify the faulty line, and can effectively solve the current poor reliability and low adaptability technologies in the field of single-phase grounding fault line selection in the current small-current grounding systems problem. This work is supported by the National Natural Science Foundation of China (No. 51974151) and the Liaoning Provincial Natural Fund Guidance Project (No. 20180550438).