Abstract: In order to investigate the effect of inhibiting montmorillonite hydration swelling on coal slurry filtra-tion, the filtration of coal slurry containing montmorillonite was carried out under inhibitory and non-inhibitory state, and the potassium chloride and three methyl benzyl ammonium chloride (TMBAC) were used as inhibitors.The results show that the hydration swelling of montmorillonite can be inhibited by potassium chloride and TMBAC.When the mass fraction of potassium chloride is 1.12% and the mass fraction of TMBAC is 0.4%, the anti-swelling rate of montmorillonite can reach 90%.The filtration of coal slurry containing montmorillonite carried out under inhibitory has lower filter cake moisture, shorter filtration time and larger dehydration rate, furthermore, the effect of filtration for coal slurry containing montmorillonite is better when using TMBAC as inhibitor.The hydration energies of K⁺ and C₆H₅CH₂-N⁺(CH₃)₃ is lower.Therefore, K⁺ and C₆H₅CH₂-N⁺(CH₃)₃ can adsorb on the interlayer of montmorillonite and limit the self-diffusion of interlayer hydrone and sodion.Besides, C₆H₅CH₂-N⁺(CH₃)₃ can act as a filter aid and adsorb on the surface of montmorillonite and coal particles, which will increase the hydrophobicity of montmorillonite and coal particles.