Abstract: With the advancement of mechanized coal mining, raw coal feed exhibits characteristics of high ash content and clay-rich gangue, resulting in the generation of large quantities of difficult-to-settle high-ash coal slime water during wet coal processing. This high-ash slime is characterized by fine particle size, high clay content, and strong surface electronegativity. Its colloidal stability primarily stems from hydration repulsion caused by surface hydration films and electrostatic repulsion between charged particles. These microscopic interactions severely constrain the sedimentation, clarification, and dewatering efficiency of coal slime water. Therefore, in-depth investigation into the surface hydration properties of coal slime particles holds significant theoretical importance for addressing coal slime water treatment challenges.This paper introduces fundamental theories of particle surface hydration, elucidates the formation mechanism of hydration films at water-particle interfaces at micro/nano scales, and discusses their decisive role in determining interfacial properties. It examines the influence of both particle surface characteristics and solution properties on hydration film structure and thickness, analyzes surface hydration features of predominant fine particles in coal slime water, and reviews advanced characterization techniques including atomic force microscopy, infrared spectroscopy, nuclear magnetic resonance, molecular vibrational spectroscopy, rheometry, and quartz crystal microbalance, along with research methodologies such as Einstein's viscosity equation and molecular simulations. Finally, it prospects the application potential of hydration film manipulation and advanced characterization technologies in coal slime water treatment.