Abstract: As a new type of underground filling material, high water expansion slurry can effectively solve collapse problem caused by surface subsidence after underground coal seam mining. This article describes the meaning of slurry viscosity and detection methods in slurry preparation process, on this basis, it also introduces the realization of slurry preparation process control system. The system, taking PLC as the core and the fuzzy algorithm as controller, realizes the automatic control of slurry preparation process and improves the quality of the slurry preparation.