Abstract: The adsorption of negative charge on kaolinite particles surface is the main reason that causes coal slime water settle difficult.By studing adsorption dynamics of Ca²⁺,Mg²⁺,K⁺ and Na⁺ on kaolinite,adsorption tests of single kind of ions on kaolinite,competitive adsorption in two kinds of ions and four kinds of ions were carried out.The concentrations of metal ions in different conditions were measured using ion chromatography,and then adsorption amount of metal ions on kaolinite were calculated.The result shows that the adsorption amount of metal ions on kaolinite is increasing until the adsorption reached equilibrium after 90 minutes,the order of adsorption amount of single kind of metal ions on kaolinite is Ca²⁺>Mg²⁺>K⁺>Na⁺,and the competitive adsorption in two kinds of ions and four kinds of ions also agree with this rule.This study will provide a theoretical basis for water chemistry regulation technology of coal slime water flocculation and sedimentation treatment technology.