Organo-montmorillonite(OMMT)/Styrene-butadiene-styrene(SBS) modified bitumen nanocomposites were prepared by melt blending. The microstructures of OMMT/SBS modified bitumen were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM), respectively. The effect of OMMT on ultraviolet (UV) aging properties of SBS modified bitumen was investigated. FTIR and XRD analyses indicate that the OMMT/SBS modified bitumen forms an intercalated structure. It is observed that the phase contrast between the dispersed domains and the matrix is inverted in SBS modified bitumen, which is decreased with the introduction of OMMT according to AFM analysis. As a result of UV aging, both viscosity aging index and softening point increment of OMMT/SBS modified bitumen decrease significantly. There is a single phase trend in the morphology of the bitumen after aging, which is accelerated by the existence of SBS. However, these changes can be effectively prevented under the influence of OMMT, indicating the good UV aging resistance of OMMT/SBS modified bitumen. (C) 2011 Elsevier B.V. All rights reserved.