A method for identifying a lightning fault of an overhead transmission line (OTL) comprising determining a polarity of a travelling wave of each of three ABC phases subsequent to a single phase outage of the OTL. If the polarity of each phase is the same, the outage is a lightning fault and its type a back flashover; if not the same, proceed to the second step to determine a current change rate R of the fault phase. If R is larger than a threshold value, the outage is a lightning fault and its type a shielding failure; otherwise, the outage is a single-phase grounding fault. A system for identifying the lightning fault which comprises successively at least a group of fault detectors, a wireless communication module, a remote monitoring master station which adopts the above method to determine the fault type of the overhead transmission line.