In this paper, based on the insufficient reliability of the existing wire routing methods for single-pole ground faults in DC distribution networks, the previous method of wire routing based on transient quantities is improved with controllable steady-state quantities. A single-ended DC distribution network model with a modular multilevel converter (MMC) as the core is established. By injecting a sinusoidal signal into the MMC, the response waveform to the sinusoidal signal is obtained at the line, and the conclusion that the faulted line is an inductive zero-mode impedance and the non-faulted line is a capacitive zero-mode impedance is obtained, and the faulted line of the DC distribution network can be selected based on this principle. Among the influencing factors of the optimal frequency of the sinusoidal detection signal, the size of the transition resistance and the response speed of the MMC are taken into account, and the amplitude and injection time of the sinusoidal waveform is given on the basis of not affecting the normal operation of the power grid.