In order to eliminate traveling wave wave velocity uncertainty and the error from the influence of line sag on the traveling wave fault location of double-ended transmission lines, a three-point positioning method is proposed to add a detection point at a certain position in the middle of transmission line.Firstly, the current traveling wave signal is phase-mode-converted to obtain mutually independent linear mode components.Secondly, the obtained linear mode component is subjected to wavelet analysis, and the time from traveling wave head to each measuring point is detected.Finally, the corresponding formula is substituted to calculate the fault distance.The simulation results of MATLAB show that the method is not affected by the factors such as transition resistance, traveling wave velocity and fault types and so on.The method, with small error range for detected distance and with simple principle, has high accuracy and good applicability.