Boron mud, as a waste of the boron industry, has not been effectively utilized and poses great harm to the environment. In this study, boron mud treated by high-temperature calcination was used as raw material to prepare magnesium oxysulfide cement. The effects of different calcination conditions on boron mud and the influences of boron mud calcination temperature, holding time, and content of calcination products on the mechanical properties, phase composition, and microstructure of magnesium oxysulfide cement were investigated. The results show that MgCO3 in boron mud can be decomposed to obtain highly active MgO at 700 ℃ after holding for 2 h, and the burning loss rate of boron mud is maintained at 23.50%, while the hydration activity reaches the highest at 24.64%. Magnesium oxysulfide cement prepared with 45% boron mud content under calcination conditions of 700 ℃ and holding for 2 h has the best mechanical properties. The bulk density is 1.7 g/cm3, the 28 d compressive and flexural strengths are 59.0, 8.0 MPa.