Abstract: The interfacial properties between three types of coal slags (A, J1 and J2 with various base/acid ratio) and two refractory materials (mullite and corundum) were studied. The results indicate that the slag A has good wettability on both of refractory materials. While, the slags J1/J2 have experienced the process from incomplete wetting to whole wetting. The contact angles decrease with increasing of interface width of slag and refractory materials (S-R). The contact angles of J1 on mullite decrease with increasing of inclination angles from deformation temperature to 1 520 ℃, but significantly increase when the inclination angle is 20°. The SEM-EDS analysis show that the quantity of slag A permeating into the refractory material is more than that of J1 slags because of interfacial reaction. The infusion and acid-base reactions are the key factors for the refractory corrosion.