A distribution network with distributed generation is an important component of the new power system. However, the access of distributed generation leads to complex fault patterns. In particular, the single-phase fault characteristics are further weakened under the neutral via arc suppression coil grounded system, resulting in the serious difficulty of single-phase fault location. To address the problems of insufficient sensitivity or difficulty in extracting and processing the characteristics posed by existing methods, the zero-mode current and its distribution characteristics in the transient process of a single-phase fault in the active distribution network are analyzed. It is found that the transient zero-mode currents are always oscillating and decaying with opposite polarity upstream of the fault and in the non-faulted section. Then, the skewness coefficient is introduced to characterize the oscillating and decay of the transient zero-mode current. A single-phase fault location criterion based on the skewness coefficient of the characteristic transient zero-mode current is constructed, and a sensitive location method of the single-phase fault section in the active distribution network is proposed. The theoretical analysis and simulation results show that the method is able to locate single-phase faults in active distribution networks on the basis of significantly reducing the difficulty of fault feature extraction and processing. It has the advantages of simple setting calculation and strong anti-communication interference ability, providing a theoretical basis for the rapid and safe disposal of single-phase faults in the new generation of distribution networks. This work is supported by the National Natural Science Foundation of China (No. 51877018).