The invention belongs to the technical field of cement preparation, and particularly relates to a calcium silicon magnesium phosphate cement and a preparation method thereof. Diammonium phosphate, yellow phosphorus slag, light burning powder of magnesium oxide, dry-based phosphogypsum, borax, fluorosilicate and sodium hexametaphosphate are used as raw materials, to reuse the yellow phosphorus slag and reduce process costs. The raw materials are designed at a reasonable proportion and subjected to treatment of crushing, mixing, drying and other processes, so that the compatibility between the components is improved; compared with the prior art, the calcium silicon magnesium phosphate cement provided by the invention avoids a defect of great shrinkage of magnesium phosphate cement, shortens cement setting time, and improves strength of the cement, wear resistance and other physical properties.