A precise and robust fault location method based on positive and negative sequence fault components for transmission lines is proposed, with synchro phasor data. This method utilizes the information of current and voltage synchronously measured by the phasor measurement units at both ends of the line, and does not require line parameters. The line parameters are not constant due to load and weather conditions and other factors, which aff ects the accuracy of most ranging algorithms relying on line parameters. For asymmetric faults, positive sequence and negative sequence fault components are used to locate the fault location, and for symmetric faults, positive sequence fault components are used to locate the fault location. The method is added to the synchronization data self-diagnosis procedure to further improve the accuracy of positioning. Then, the paper presents the method derivation and the simulation results by PSCAD/EMTDC under diff erent path resistance, fault type, fault inception angle, load current, and line transposition, measurement error. The simulation results prove that the method effi ciently and accurately determines the fault location.