Abstract: The line structure and fault characteristics of flexible DC transmission system put forward higher requirements for the accuracy of line fault location and location scheme. According to the characteristics of bipolar short circuit fault, a fault area location based on BP neural network theory is proposed. The fault distance measurement of DC transmission line based on the least square method is realized by using the method of line parameters to realize the synchronization of recording data at both ends. The scheme uses the least square method to synchronize the fault recording data in time to reduce the error of fault location results. After synchronization, the data is applied to the transmission system analysis and fault location, providing reference for rapid fault location and subsequent power supply restoration after the system line fault occurs. Finally, the reliability and credibility of the proposed fault location process and the fault location scheme are verified through building the system on the PSCAD platform and a large number of simulations.