Abstract: In order to investigate the resistance characteristics of unidirectional carbon fiber/epoxy prepreg subjected to lightning currents, low simulated lightning currents of 10/350 μs waveform were applied on the unidirectional carbon fiber/epoxy prepreg. The direct current (DC) resistance data of the unidirectional carbon fiber/epoxy prepreg before and after the tests were measured adopting the four-probe method. The SEM and Raman spectrum were used to characterize the morphology and phase structure of carbon fiber/epoxy prepreg before and after the test. The causes of the DC resistance change were analyzed. The results show that the DC resistance of the carbon fiber/epoxy prepreg does not change monotonously with the increase of lightning current, but tends to decrease first and then increase. This trend is the combined effects of graphitization, epoxy insulation deterioration, fiber fracture and tunnel effect.