Travelling-wave location method which can locate transmission faults precisely is widely used in transmission networks. However, only the electrical distance is given generally during practical applications. If the influence of span and sag is not taken into account, notable deviation between the calculation result and the actual fault location especially in long-distance transmission line will impact. In complex terrain areas, this misjudgment of fault locations will greatly affect the efficiency of inspection and overhaul. To handle this, an accurate fault location method considering the influence of span and sag is proposed in this paper. Firstly, the Haversine formula is used to compensate the transmission line span. Then, considering the structural parameters of the tower and the actual temperature, a catenary model is built, and the electrical distance can be compensated via the compensated span length. Finally, a double-terminal traveling wave positioning method is utilized to obtain the precise location of the fault. According to the actual parameters, a 500 kV transmission line is built in PSCAD/EMTDC, and different faults are set at different positions. Multiple sets of experimental results show that this method can improve the accuracy of the traveling wave location method.