In order to study the effect of C9 petroleum resin(C9PR) on SBS modified asphalt, C9PR/SBS composite modified asphalt was investigated. The microstructure and rheological properties of C9PR/SBS composite modified asphalt were characterized by fluorescence microscope and dynamic shear rheometer. The results show that C9PR can promote the uniform dispersion of SBS in asphalt, improve the compatibility of SBS with asphalt and the storage stability of SBS modified asphalt, increase the softening point, 135℃ rotational viscosity and complex shear modulus(G) of modified asphalt, reduce ductility, penetration and phase angle(δ). Meanwhile, the addition of C9PR can improve the anti aging performance of SBS modified asphalt.