This study examines the healing capacity of an asphalt mixture after the introduction of an iron-based additive (iron slag). It is hypothesized that iron-based additives can facilitate healing of asphalt pavement by enhancing the thermal conductivity of the asphalt pavement. To study the healing capacity of asphalt mixtures containing iron slag, specimens with various amounts of iron slag additive were prepared and tested using a semi-circular bending test. Healing tests were performed on samples with different crack lengths, which each crack length representing a specified damage degree. Infrared heating was used to condition each specimen to facilitate healing. The significance of factors such as the amount of iron slag, the healing temperature, the healing time, and the damage degree were studied through grey correlational mathematical analysis. Among the samples tested, the optimal healing content of iron additive was 2%, the optimal healing temperature was 60 °C. Samples with a damage degree of 30% recovered about 59% of their original structural strength. And the results from grey relational analysis showed that the extent of damage was the most influential factor, followed by healing temperature, dosage of iron slag, and healing time.