The composite modified asphalt was prepared by adding different use levels(by mass) of SBS to TB asphalt(terminal blend asphalt). Laboratory test was conducted to investigate the enhancement effect of SBS on pavement performance of TB asphalt. The strengthening mechanism of SBS on pavement performance of TB asphalt was analyzed. Results show that SBS can improve softening point and ductility of TB asphalt effectively, and reduce the penetration. By mixing with 30% SBS, the PG grade of TB asphalt can reach 70 28 from 58 28. TB+30% SBS composite modified asphalt mixture shows advantage in stability at high temperature over the 45% SBS modified asphalt mixture. TB+30% SBS composite modified asphalt shows good performance at both high and low temperature. Considering the fatigue property, self healing compensation effect and stability at high temperature under the same objective void ratio, the ranking of combination performance of various asphalt mixtures is as follows TB+30% SBS composite modified asphalt mixture＞45% SBS modified asphalt mixture＞TB asphalt mixture＞base asphalt mixture. SBS，crumb rubber and base asphalt are well cross linked to form a homogeneous and dense system.