The variation of ice particles due to growth, breakage, and aggregation usually occurs in a dynamic ice slurry storage system, which is extremely important for ensuring a safe and steady cold supply. However, the variation characteristics of ice particles in a dynamic ice storage system are still far from being fully understood. This investigation performed experimental and numerical studies based on the population balance model and the kinetic theory of granular flow. The experimental results clearly demonstrated that the growth and agglomeration of particle in slurry were highly obvious. Generally, the growth rate of ice particles gradually decreased as the storage time increased. When the concentration of the ice packing fraction and carrier fluid solution increased, the growth rate of ice particles increased. The performance of the prediction model was satisfactory in capturing the characteristics of ice particle variation. It was significant for the design of ice slurry storage devices and for improving the efficiency of district cooling systems.