High voltage flexible DC transmission uses the overhead line. This makes it difficult to avoid faults in a complex environment. Fast and accurate fault location can shorten the time of fault clearing, something which is very important for fast power supply recovery. The existing ranging algorithms rely on transient wave head identification, and the ranging accuracy will decrease when disturbed. Based on a distribution parameter model, this paper calculates the voltage and current along the line through the telegraph equation in the time domain, and then forms the ranging criterion according to the feature that the resistance value at the fault point is relatively stable. Since the coincidence time of DC circuit breakers on both sides of the transmission line is not consistent, the system on the overlapping side will continue to feed the short-circuit current to the fault point. Therefore, ranging can be realized through a single terminal. The proposed ranging method requires no communication, which is suitable for various fault types and requires short window length, and can withstand transition resistance and noise. Finally, a four-terminal HVDC ±500 kV model is built in PSCAD/EMTDC simulation software and the simulation results verify the accuracy and applicability of the proposed ranging algorithm. This work is supported by the National Key Research and Development Program of China (No. 2018YFB0904100) and the Science and Technology Project of State Grid Corporation of China (No. SGHB0000KXJS1800685).