The phase-frequency characteristic of a distribution line in a zero-mode network is analyzed in detail to solve the problems of inaccurate selection of characteristic frequency band near the zero crossing point of phase voltage and protection device sampling out of sync in a non-effectively grounded system. A new line selection method based on characteristic frequency band transient reactive power correlation detection is put forward in this paper. First, cross wavelet transform is carried out on each outgoing line transient zero-mode current and bus differential zero-mode voltage. The region with strong correlation and stable phase difference is taken as the time-frequency window of fault line selection. Then, the transient reactive power is calculated with the amplitude and phase information of the transient voltage and current signal in the time-frequency window. Finally, based on the characteristics that the flow direction of transient reactive power of fault line within the feature band is opposite to that of non-fault line, the correlation of transient reactive power of each outgoing line is detected with the cross-correlation function algorithm to determine the fault line. Theoretical analysis and simulation results indicate that the proposed method will not be affected by factors such as initial angle, synchronization error and noise interference of the fault, and has strong adaptability to high resistance and arc grounding. This is suitable for single-phase grounding fault line selection of a distribution network connected with a distributed power supply. This work is supported by the Key Project of National Natural Science Foundation of China (No. 51637005).