［Purposes ］ To address the two major technical bottlenecks of poor volume stability and insufficient interfacial moisture stability when steel slag is used as aggregate in asphalt mixture，this study aims to explore effective pretreatment processes to promote efficient resource utilization of steel slag in road engineering.［Methods］ Five pretreatment processes，namely natural aging，steam treatment，acetic acid immersion，oxalic acid modification，and polyvinyl alcohol （PVA） treatment，were used to pretreat steel slag.The pretreatment effects were systematically evaluated through macroscopic tests such as water immersion expansion and freeze -thaw cycle mass loss，along with microscopic analysis.Subsequently，modified steel slag was used to prepare SMA -13 asphalt mixture，and its road performance was examined.［Results］ Oxalic acid treatment significantly reduces the water immersion expansion rate and freeze -thaw cycle mass loss rate of steel slag.Scanning electron microscope （SEM） analysis shows the formation of dense precipitates on its surface，which effectively enhances the volume stability.PVA treatment forms a reticular organic coating on the steel slag surface，noticeably improving its water absorption and adhesion to asphalt.The asphalt mixture prepared with these two modified steel slags exhibits significantly better high -temperature stability，moisture stability，and raveling resistance than that prepared with merely naturally aged steel slag.［Conclusions ］ From macroscopic and microscopic perspectives，this study reveals that pretreatment can improve steel slag performance through a “surface modification and interface strengthening ” mechanism.It verifies that the the mixture exhibits excellent road performance，providing theoretical support and technical foundation for the large -scale resource utilization of steel slag in asphalt pavement.