The conductance of clay intercalation compounds as solid electrolytes is studied. Six typical montmorillonite clays from China are purified, and a hectorite clay is synthesized. Smectite intercalation compounds (SIC) have been prepared by ionic exchanges in smectite structure interlayers. The differences in layer structure and compositions of smectite have an effect upon the conductivities of SIC. The higher the interlayer charges of smectite structure, the better the conductivities of SIC. The cationic substitution of structural cations has an influence on the migration of ions in interlayer. It is found that the migration of iron becomes easier in the case of a replacement in the lattice octahedra.