Abstract: According to the characterization of XRD and the choice of structure unit,the crystal lattice parameters of inorgano-montmorillonite (K-MMT and Mg-MMT) have been determined.The binding energies existing between layers of K-MMT and Mg-MMT have been calculated and analyzed by Empirical Electron Theory of Solids and Molecules (EET) respectively.PMMA/K-MMT and PMMA/Mg-MMTcomposites have been prepared via common emulsion polymerization,characterized by XRD respectively.The research of EET shows that the binding energies between layer surface and adsorptional K+ (K-MMT) and Mg2+ (Mg-MMT) are 92.32 kJ/mol and 0.06 kJ/mol respectively.Combined with the order of metal activity (K>Mg),it can be observed that compared with K-MMT,Mg-MMT is easier to disperse in the polymer matrix in the shape of single layer.The analysis of XRD shows that the distribution of K-MMT in PMMA is uneven with large agglomeration,while that of Mg-MMT in PMMA is homogeneous,which agrees with the conclusion obtained by EET.