Transient signals caused by lightning strikes on transmission lines may interfere with the distance measuring devices relying on traveling wave. Therefore, it is significant to identify lightning interference from faults to improve the accuracy of the measuring devices and reduce the maintenance workload. In order to make use of the global fault message and avoid the signal interference generated by time-frequency transformation, this paper refers to the approximate entropy algorithm to research the line-mode components of lightning and short-circuit fault transient current in the time domain and finds that both entropy neatly differ in an order of magnitude. But it cannot distinguish between lightning interference and lightning fault. Therefore, takes advantage of the integration algorithm which is widely used in signal processing to further analyze the lightning signal and realizes that standard deviation of the integration value upper and lower timeline is obviously distinct. We achieve the identification of lightning interference, lightning fault and short-circuit fault by integrating this two methods. Numerous PSCAD simulation results demonstrate that the proposed method is valid and applicable regardless of the fault location, fault condition and interference noise.