The fluidized backfill technology has become an important method for safe and efficient mining and clean utilization of coal-based solid waste. In order to explore the influence of different particle size distributions on the preparation and working characteristics of slurries, a study was conducted on coal gangue from a mine in Inner Mongolia, using a combination of scanning electron microscopy, XRD diffraction, and indoor experiments. The study analyzed and compared the state of slurries, diffusion parameters, and other factors for different particle size distributions and concentrations, revealing the impact of particle size distribution on the performance of backfill slurries. The research findings indicate that when the powder content is 19.401%, the slurry exhibits optimal performance, with an ideal concentration of 70%. At this concentration, the slurry has a slump value of 28cm and a maximum diffusion distance of 45.9cm, demonstrating the significant role of coal gangue particle size distribution in the preparation and working characteristics of the slurry.