Fatigue damage self-monitoring mechanism of graphite modified asphalt-based composite materials is demonstrated in this paper, as damage (occurring in the 70% of fatigue life) caused the volume electrical resistance to increase irreversibly. Results showed that when the initial resistance is relatively high (10k), the resistance variation sensitivity of microcrack is lower, but it has relatively high sensitivity to microcrack when the initial resistance 1k. The longer the loading time, the greater the damage, and the greater the resistance increases monotonically occurred. The resistance increase is attributed to the proximity effect, microcrack and the disconnection of conductive paths due to shear strength of aggregates. The self-monitoring mechanism of damage is the resistance change aroused by the variation of interior structure.