Star S-SBR can be produced in one step by a kind of new anion polymerization technology in which modified naphthalene lithium acted as the initiator and SnCl, acted as the coupling agent. The influence of the molecular structure of star S-SBR on its mechanical and dynamic properties was studied. The results showed that Star S-SBR, with styrene (St) content of 20-25% and vinyl (Bv) content of 45%, and molecular weight for one arm (MW/arm) of 8 ten thousand, has good mechanical properties, low rolling resistance and high wet grip. The end of the S-SBR molecular chain was coupled by a coupling agent, which resulted in low internal friction loss. The bound rubber content of star S-SBR-carbon black compound was larger than that of linear S-SBR compound. Experiments showed that the Sn-C key in star S-SBR broke easily under shear action and formed a free group, and the free group bonded immediately with the active group on the surface of a carbon black particle. (C) 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2311-2315, 2003.