The propagation process of the fault transient traveling waves and the external injected pulse signals in the grounding electrode lines of high-voltage direct current (HVDC) transmission system in monopole operation mode is analyzed. On this basis, a fault location scheme for grounding electrode lines is presented based on the combination of pulse injection method and single-ended fault travelling wave method. The scheme identifies firstly whether the electrode lines is faulted by monitoring the electrode lines fault transient traveling wave on the converter station DC neutral bus. After the circuit fault transient process finished, a pulse signal is injected from the neutral bus. The preliminary result is obtained according to the pulse injection method by which the fault location section is determined. Then, according to the fault location section, the second result is obtained by the single-ended fault travelling wave method. The final measured result is the average of two location results. On the PSCAD/EMTDC simulation platform, the monopole HVDC transmission system simulation model is built for fault location analysis of grounding electrode lines. Matlab is used to process the simulation waveform data, indicating that the proposed fault location scheme for grounding electrode lines is feasible.