A fault segment localization method of resonant grounding system based on matrix beam algorithm is proposed. Analyzing the difference of the positive-sequence real-time current in the fault-added state between the upstream and downstream of the fault point when a single-phase ground fault occurs in a small-current grounding system. The criterion of the fault section is that the positive-sequence real-time current mainly flows through the upstream of the fault point. On this basis, the matrix beam algorithm is used to extract the instantaneous positive-sequence real-time power frequency amplitude of each detection point on the fault line of the resonant grounding system, and the area between two adjacent detection points with the largest amplitude difference on the fault path is the fault section.In addition, the effectiveness of the method is verified by the built matlab model.