The invention discloses a power transmission line fault phase selection method. The method comprises firstly measuring the three-phase current sudden changes at the mounting position of a current transformer of a power transmission line in real time, and then performing the fault phase selection according to the fact that the ratio between each two changes has different mathematical characteristics under different types of power transmission line faults. The power transmission line fault phase selection method is provided with high phase selection sensitivity at a weak power side and even under the conditions that a single phase ground fault through highresistance occurs and the system operation mode changes a lot, thereby being capable of providing correct and accurate fault phase information for distance protection and the correct action of automatic reclosing.