The difference of physical and chemical properties of slag has a great effect on the performance of new gypsum slag sulphoaluminate cement (SAC-GS). Therefore, three typical slags for production were selected to try to construct the relationship between the composition, structure of slag and the macroscopic properties of SAC-GS in multiple dimensions. The mineral composition, element composition and the existence state of each slag were compared and analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The hydration process of each hardened cement paste sample was analyzed by Scanning electron microscope (SEM), XRD and other methods, and the compressive and flexural strength of each sample at different hydration ages were tested, and the early hydration heat release evolution and pore size distribution were compared. The results show that the slag with higher aluminum content and higher reactivity has faster strength development, higher hydration degree and denser pore structure of cement sample. Slag with high aluminum content should be selected for the preparation of SAC-GS.