Styrene-butadiene rubber (SBR) nanocomposites were prepared from organically modified montmorillonite (OMMT). To enhace the dispersion properties of OMMT in SBR matrix, polybutadiene was modified with tetramethyl siloxane substituted with benzylamine, and the master batches of those were prepared by a solution process using tetrahydrofuran. SBR/master batch nanocomposites could be obtained by melt-compounding followed by hot-press vulcanization. Xray diffraction (XRD) studies revealed that the interlayer distances of OMMT were increased and the nanocomposites had the intercalated and exfoliated structures of OMMT by the nanocomposition of SBR with the master batch. Mechanical and dispersion properties of the nanocomposites from the master batch are superior to those of nanocomposites without master batch.