The main reasons affecting the fluidity of P·O42.5 cement slurry were analyzed, and measures to improve the fluidity of P·O42.5 cement slurry were proposed. It was adding 3% coal gangue for raw meal batching; adjusting the raw materials and control indicators for cement batching, using modified phosphate gypsum and desulfurized gypsum in a 1:1 combination; optimizing and adjusting the grinding process of the open-circuit mill and improving the feeding of the powder separator. In this way, the specific surface area and temperature of the grinding cement were reduced, and the management of cement in and out of the warehouse was improved.