The influence of MgO on the composition, structure and properties of alite-calcium strontium sulphoaluminate cement were investigated by means of X-ray diffraction, SEM–EDS and light analysis. The results show that when the mass fraction of MgO is 1~5%, the early strength of cement can be enhanced significantly. The optimal content of MgO in the cement clinker is 2% and the compressive strengths of the cement at 3, 28 d are 64.3, 103.6 MPa respectively. A suitable amount of MgO can promote the formation of C1.5Sr2.5A3 , while the formation of C1.5Sr2.5A3 can be hindered if the content of MgO is excessive. The existence of MgO can improve the formation of C3S, increasing the mechanical property of the cement. Compared with the Portland cement, alite-calcium strontium sulphoaluminate cement has a higher capacity to dissolve MgO, which indicates that low-quality high-magnesium limestone can be efficiently used in the cement production.