A flexible DC transmission line fault location scheme is proposed to address the problem of signal susceptibility to noise interference and poor transient resistance capability in the fault location process, in which wavelet transform (WT) for noise cancellation and variational mode decomposition (VMD) are used. First, the fault signal is denoised using a Logistic function-based cycling displacement wavelet threshold. Then a snow ablation optimizer (SAO) and VMD are used to effectively decompose the signal. Finally, S-transform (ST) is conducted on the decomposed high-frequency components, and the amplitude curves at the corresponding frequencies are selected for wavehead calibration. In addition, a distance measurement algorithm independent of wave speed is proposed. Simulation verification is performed by building a double-ended flexible DC system in the PSCAD/EMTDC platform. The results show that the proposed scheme not only requires low sampling rate but also has the ability to withstand 300  transient resistance and 30 dB noise, so it is able to accurately measure distances at different fault locations.