Coal gasification slag (CGS) is rich in silicon and aluminum elements, which has the potential to be used as a precursor of cementitious materials. However, the particle morphology of CGS is rough and the activity is low. In this study, in order to solve the issues of low activity and difficult utilization of CGS, the technical feasibility of using CGS as a partial substitute for blast furnace slag (BFS) in the preparation of SSC was explored. The microstructure of the hydrated products of SSC was characterized and analyzed using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, energy dispersive spectrometry and other microscopic testing techniques. The results show that CGS as a raw material for the preparation of SSC, can provide the silicon and aluminum elements needed for initial hydration and drive the hydration reaction of SSC. With the increase of the dosage of CGS, the compressive strength of SSC sand shows a gradual decrease, while the effect on flexural strength is small. The optimum dosage of CGS is 20% ( mass fraction), under this dosage, the 28 d flexural strength of cement sand specimen is the largest, and the compressive strength also reaches 43. 9 MPa. The hydration products of SSC are mainly hydrated calcium silicate, hydrated calcium sulfoaluminate and other gels. The results show that CGS can be used to prepare SSC by partially replacing BFS.