Four styrene–butadiene–styrene(SBS) modified bitumens had been prepared by a base bitumen, a crosslinking agent and four SBS copolymers which differ in styrene blocks content and molecular configuration (radial or linear) under the same experimental conditions. Conventional properties, morphology, thermal behavior and microstructure were investigated by means of conventional tests, fluorescence microscopy, differential scanning calorimetry (DSC), and Fourier transform infrared (FT-IR) spectroscopy. In terms of linear SBS polymers, the SBS molecule with the styrene content of 30% has a perfect dispersion and complete stretching in bitumen matrix, and in this case, the conventional properties and thermal stability of bitumen are enhanced substantially. However, the star SBS polymer due to long branched chains forming the preferable steric hindrance to enhance the intensity of base bitumen, plays a more important role in improving the conventional properties of base bitumen than linear SBS polymers. Furthermore, the FT-IR spectra indicate that, the main bands assignations of four modified bitumens are identical and the significant variation is the peak intensity. And a noncomplete crosslinking reaction happens between the bitumen and each SBS polymer, which can efficiently prevent excessive cross-linking from affecting the intrinsic bitumen characteristics. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40398.