Many surface processes of clay minerals require in-depth understanding of their surface electricalproperties, such as surface charge density, surface potential distribution, etc In this paper, electrostaticforce microscopy (EFM) and Kelvin probe force microscopy (KPFM)were used to study the surfacecharge densities, surface potentials, electric field intensities, and electric field force gradients of threecommon clay minerals: kaolinite, montmorillonite, and illite. The properties were directly imaged,and the average surface permanent charge densities of kaolinite, montmorillonite, and illite wereobtained to be −0.0060, −2.136, and −5.456 μC m−2, respectively. In addition, a good linearrelationship was found between the surface charge densities obtained by KPFM and the layer chargescalculated from the mineral chemical formulas of three clay minerals.