Abstract: In order to explore the influence mechanism of lattice Mg（II）impurities on the surface charge characteristics of kaolinite, Mg（II）doped kaolinite is taken as the research object. The surface charging characteristics of Mg（II）doped kaolinite are systematically studied by means of Density Functional Theory (DFT) and classical Molecular Dynamics（MD）. The molecular simulation results are verified by Zeta potential testing of Mg（II）doped kaolinite samples. The results of DFT show that: after Mg（II）doping, the Mg and adjacent oxygen atoms have formed new bonds, which makes the charge on the surface of kaolinite rearrange and present a negative charge. MD results show that the negative surface charge of kaolinite (001) surface increases and the surface potential decreases with the increase of Mg（II）doping. The results of Zeta potential test show that the deprotonation on kaolinite basal and edge surfaces gradually increases with the increase of solution pH value, and the surface potential of kaolinite surfaces with different Mg（II）doping amounts gradually decreases, and the negative surface charge of Mg（II）doped kaolinite is significantly stronger than that of pristine kaolinite. The experimental results are in good agreement with the molecular simulation results, which verifies the accuracy of the simulation. The influence mechanism of Mg （II）doping on the charge of kaolinite is mainly that the negative charge characteristics of kaolinite surface are significantly enhanced, and the electrostatic repulsion between particles is enhanced, resulting in difficult agglomeration of fine kaolinite particles. The research can provide further theoretical support for the efficient sedimentation of coal slurry.