The morphological structure, glass transition, mechanical properties, and dynamic mechanical properties of star-shaped solution-polymerized styrene-butadiene rubber (SSBR) synthesized by a multifunctional organic lithium initiator and SiO2-SSBR composite (N-SSBR) prepared through adding a small amount of nanosilica modified by silane coupling agent to star-shaped SSBR synthetic solution and co-coagulating, and their nanocomposites filled with 20 phr nanosilica were investigated, respectively. The results showed that the silica particles were well dispersed with nanosize in N-SSBR, which glass-transition temperature (T-g) was 2 degrees C higher than SSBR. N-SSBR/SiO2 nanocomposite exhibited lower Payne effect and internal friction loss, higher mechanical properties, and its T-g was 2 degrees C higher than SSBR/SiO2 nanocomposite. N-SSBR might promote the dispersion of nanosilica powder in matrix and could be applied to green tire tread materials. (C) 2008 Wiley Periodicals, Inc.