In this chapter authors present processes of obtaining montmorillonite modified by polyionenes. Intercalation of macromolecular polymer of a quaternary ammonium salt in montmorillonite intercrystalline space is exhibited to be accompanied by increasing interlayer distances from 1.08 nm to 1.67 nm. The technique of synthesis of montmorillonite modified with polyionenes is proposed. Optimal conditions for sorption of polyionenes molecules by montmorillonite are stated as follows: the concentration of aqueous dispersion of montmorillonite equals 1%, the temperature of the reaction medium is 40 ºC, the montmorillonite-polyionene ratio is 3: 1, the processing time is 24 hours.