The microstructure of the refractory material is closely related to its properties, and the wettability between the liquid phase and the crystal phase in the refractory material is an important factor determining the microstructure. In this study, the wetting behavior of different C/S silicate impurity phases on solid MgO substrates at 1 450 °C was explored by the sessile drop method, and the spreading mechanism of the system was discussed. The driving force of the wetting process is the dissolution of the MgO substrate. At 1 450 °C, the equilibrium contact angles of M1-M3 were measured to be 0, 4 ° and 11 ° respectively. The M4 sample did not wet and the contact angle hardly changed.