Abstract: The influence of grinding time on specific surface area of steel slag powder was studied in this paper. The particle size distribution and particle morphology were investigated by laser particle sizer (LPS), X-ray diffraction (XRD). And the influence of steel slag powder ground with different time on compressive strength of concrete was studied. The results showed that the grindability of steel slag was poor. With the increase of grinding time, the proportion of micro particles in the steel slag powder was gradually increased and the compressive strength of concrete also gradually improved. Accordingly, the grinding cost also increased. The suitable grinding time of steel slag powder was 90 min, and the specific surface area could reach to 650 m²/kg.