Abstract: The regulation of hydration phenomenon on clay mineral surfaces is the key to improving the efficiency of coal resource utilization and coal slime water recycling in China. The interfacial hydration characteristics directly determine the dispersion, aggregation and solid-liquid separation effects of fine-grained minerals. Kaolinite, as the clay mineral with the highest content and the most significant influence in the coal selection system, has anisotropic surface properties, which result in significant differences in physical and chemical properties on the surface of kaolinite particles in different directions. This is a core scientific issue that needs to be urgently addressed to enhance the level of coal slime water treatment. With kaolinite, the dominant clay mineral in coal preparation processes, as the research object, the effects of solution conditions on the hydration characteristics of the Al basal plane, Si basal plane and edge surface of kaolinite were systematically investigated on the basis of the EDLVO theory, using atomic force microscopy colloidal force measurements combined with force curve fitting. The results showed that the surface hydration force constant of kaolinite is independent of the chemical composition of the mineral surface, and it is independent of solution pH, while the attenuation length the shows significant differences, following the order of Al basal plane > Si basal plane > edge surface. Under the research system of this study, it was found that hydration force and DLVO force are superimposable. Based on the hydration characteristics of the kaolinite surface, a microscopic mechanical calculation model of kaolinite self-polymerization structure was constructed. By combining the three surface hydration force constants and attenuation length values of kaolinite, the interaction energy of kaolinite particles during aggregation under different solution conditions was calculated. Through analyzing the interaction energy of different association structures of kaolinite, the optimal solid-liquid separation conditions was predicted to be pH 5, and it was visually comfirmed by macroscopic kaolinite suspension settling tests, confirming the reliability of the microscopic mechanical model. The mechanism of surface hydration of kaolinite was revealed from a microscopic perspective, and the regulation mechanism of solution conditions on particle interactions was clarified, thus providing an important theoretical basis and technical support for the efficient solid-liquid separation of fine clay minerals in coal slime water, the optimization of coal preparation processes, and the resource utilization of coal slime water.