Abstract: By orthogonal experiments, through the analysis of the appearance, pressure-resistance strength and hydration products of steel slag and slag based cementing materials, the effect of the composite activators of calcium hydroxide and activator D on the stability and pressure-resistance strength of the cementing materials was studied. The results show that compared with the materials without activators, the composite activators significantly enhance the activity of the cementing materials and improves its stability. The order of influencing factors on the pressure-resistance strength of cementitious materials is activator D, calcium hydroxide and steel slag powder. When the mass fraction of the steel slag, the slag micropowder, the calcium hydroxide and the activator D is 40%, 53%, 3%, and 4%, respectively, the volume stability of the cementitious material samples is qualified, and the pressure-resistance strength reaches the maximum of 15.46 MPa.