Abstract: The steel slag powder is a powdery product formed by ball milling after the industrial waste is discharged from steelmaking. It has similar properties to those of cement, but its activity is poor and it needs to be treated. Through the laboratory tests, caustic soda (NaOH) is used as the activator of the steel slag powder to study the effect of the slag powder and cement mixed on the silty soil under different caustic soda contents. The results show that the early strength of the steel slag-cement solidified soil is low, and the curing effect is better at the later stage. After the caustic soda is added, the curing effect of the steel slag powder is obvious. The unconfined compressive strength of the steel slag-cement solidified soil increases first and then decreases with the increase of activator dosage. The X-ray diffraction (XRD) analysis shows that there is a monosulfated calcium sulphoaluminate (AFm) in the mixture, which can enhance the strength of the solidified soil.