To research the self-healing performance of steel slag asphalt mixtures by microwave heating, four kinds of asphalt mixtures were prepared: whole stone type, coarse stone fine steel slag type, coarse steel slag fine stone type and whole steel slag type. The thermal and electromagnetic parameters of asphalt mixtures were measured by thermal constant analyzer and vector network analyzer. The temperature distribution of asphalt mixtures was measured by thermocouple temperature sensor and infrared thermometer. The numerical simulation temperature field of COMSOL software and test temperature distribution were compared and analyzed. Finally, the self-healing performance of asphalt mixtures was evaluated by three-point bending failure test. The results show that the four asphalt mixtures have different microwave absorption and heat transfer properties, and have a certain impact on the heating rate of asphalt mixtures. The addition of steel slag greatly improves the microwave heating performance of asphalt mixtures, and the coarse stone fine steel slag in the three steel slag asphalt mixtures shows better heating uniformity. COMSOL software simulates the temperature distribution of asphalt mixtures under microwave heating. Compared with the whole stone asphalt mixtures, the self-healing performance of coarse stone fine steel slag, coarse steel slag fine stone and whole steel slag asphalt mixture increase by 1.11 times, 1.14 times and 1.11 times, respectively. The addition of steel slag improves the self-healing performance of asphalt mixture.