The invention relates to a power transmission line fault distance measurement method, a device, a positioning verification method and a system. A dual-end correlation light signal mode is mainly employed, and a distance between a fault point and a first monitor is acquired according to a value of the first time when one end receives an adjustment waveform of a first light signal, a value of the second time when the other end receives an adjustment waveform of a second light signal, spread speeds of the first light signal and the second light signal, and length of a transmission channel of the light signals. According to the method, the dual-end correlation light signal mode is employed, whatever the position of a fault point between two ends is, a problem of front and back signal identification difficulty caused by front and back signal overlapping can be solved as one end receives only one modulation waveform, accuracy of distance measurement is improved, limitation of a spatial resolution of system equipment is avoided, influence of temperature of the surrounding environment can be avoided, and higher practicality and feasibility are realized.