The invention discloses a lightning stroke detection method of an electric transmission line. The lightning stroke detection method of the electric transmission line comprises the steps that differential current of the electric transmission line at the two ends of a detection point is collected, the differential current is monitored, when the differential current exceeds a preset threshold value, it is judged that a lightning stroke event happens, and when it is judged that the lightning stroke event happens, the detection point where the lightning stroke event happens sends out an indication signal. According to the lightning stroke detection method of the electric transmission line, the differential current of the electric transmission line at the two ends of the detection point is collected, and under normal circumstances, the differential current is quite small and can be basically neglected. When the lightning stroke event happens, lightning current is quite heavy, and the differential current at the moment is quite heavy. Through the lightning stroke indication method, the difference between fault current when the lightning stroke event happens and the normal current is obvious, and therefore a lightning stroke fault can be indicated more accurately and the sensitivity is higher.