Tin-coupled star-shaped block styrene-isoprene-butadiene terpolymer was successfully synthesized by anionic polymerization. The structure character and performance were characterized by NMR, GC, GPC, TEM and DMA, and the performance of terpolymer was compared with that of other rubbers. The results indicate that the styrene units are randomly distributed in the copolymer as the St content is lower than 30%, block styrene is generated as the St content is higher than 35%. The amount of side group content of terpolymer decreases dramatically as the St content increases. In the process of copolymerization, the conversion of St, Ip and Bd increases gradually with increasing of the total conversion. The terpolymer morphology is uniform when the styrene content is low, phase-separated morphology occurs as the St content increases and DMA results shows that loss peak is broadened and moves to high temperature direction. The mechanical properties of (SIB-PB)₄Sn are equal to those of other rubbers, but the wet skid resistance is better and the rolling resistance is less, so it is an ideal rubber material for tire tread.