Abstract: The present invention relates to nanocomposite materials based on a copolymer of at least two monomers selected from the group consisting of butadiene, isoprene and styrene and a clay mineral dispersed therein, and a process for preparing them. By using an organolithium as the initiator, an organic hydrocarbon solvent as the solvent and a polar additive as the microstructure modifier by means of a classical anionic solution polymerization process, at least two monomers selected from the group consisting of butadiene, isoprene and styrene are in-situ intercalation polymerized in the presence of an organoclay, thereby obtaining a delaminated nanocomposite material which is excellent in mechanical properties, heat resistance, barrier property, chemical resistance and is well balanced in its comprehensive properties.