It is generally difficult to select high-resistance ground fault phases and fault lines in distribution networks. This paper proposes a new method of phase selection and line selection for high-resistance faults in asymmetric distribution networks based on a flexible-grounding device. First, the change characteristic of the zero-sequence current of each feeder before and after zero-sequence voltage regulation is analyzed in detail. It identifies the fault feeders using the dispersion degree of zero-sequence equivalent admittance of the faulted feeder and the healthy feeder in different regulation and control states. Thus the fault line identification function is obtained and a line selection criterion is constructed. Secondly, the fault phase is identified according to the angular relationship between the zero-sequence equivalent admittance of the feeder during the phase separation adjustment process and the ground admittance value of the feeder before the fault. The fault phase selection function is derived and the phase selection criterion is constructed. Theoretical analysis and PSCAD/EMTDC simulation show that the asymmetry of the three-phase ground admittance of the distribution network has no effect on the method proposed. Both low and high resistance ground faults have higher sensitivity in the method, the fault phase selection and line selection results are accurate, and the phase selection and line selection methods are effectively combined. This work is supported by the National Natural Science Foundation of China (No. 51737002 and No. 52037001).