The attenuation process of skid resistance of tunnel steel slag asphalt pavements was simulated by the indoor accelerating wear instrument. The skid resistance attenuation rule of steel slag asphalt mixtures (SSAM) with different contents of steel slag, different loads, and different temperatures was studied. The skid resistance attenuation progress and mechanism of SSAM was analyzed by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results show that the addition of steel slag improves the skid resistance of the asphalt mixture from final attenuation value, loss rate and decay rate. The skid resistance of SSAM shows a trend of first increasing and then decreasing with the addition of steel slag, and there is an inflection point at the 50% steel slag content. The effect of load against skid resistance is mainly reflected in the second to fifth stages of the attenuation process. The effect of temperature against skid resistance is mainly reflected in the first stage. The surface texture of steel slag aggregate is complex, and its hole structure and grading are more reasonable, which improve the adhesive property of the SSAM asphalt film and the stability of the SSAM skid resistance.