Abstract: To study the temperature distribution of steel slag porous asphalt mixture during the microwave heating and cooling processes and the heat transfer mechanism between different materials, steel slag aggregate is used to partially replace basalt coarse aggregate (4.75-9.50 mm, and 9.50-13.20 mm) in this study. The meso-scale models of asphalt mixture specimens based on three-dimensional random aggregate were built to simulate the temperature distribution of three asphalt mixtures including the conventional basalt aggregate specimens (PAC-B), un-modified steel slag aggregate specimen (PAC-US), and modified steel slag aggregate specimen (PAC-MS). The numerical simulation results were mutually verified with results of laboratory tests. Results show that the surface temperature distribution area of asphalt mortar is consistent with the aggregate surface temperature distribution area in both the heating and cooling processes, and the maximum temperature of aggregate surface is greater than that of asphalt mortar, indicating that the aggregate has a stronger wave absorption ability than asphalt mortar. During the cooling process, the aggregate can transfer heat to the asphalt mortar, and the temperature difference between them continuously decreases. For the same specimen, among the volume average temperature of aggregates (2.36-4.75 mm, 4.75-9.50 mm, and 9.50-13.20 mm), the temperature of 4.75-9.50 mm is the highest. The temperatures of PAC-US and PAC-MS are higher than those of PAC-B. The comparison between the results of heterogeneous numerical simulation and laboratory test shows a good agreement, indicating the feasibility of using heterogeneous models to simulate the temperature of microwave heating and cooling processes.