<p>The asphalt-filler interaction plays a critical role in deciding the rheological responses of asphalt mastic material. Currently, various additives have been applied to modify the asphalt binder, in which styrene-butadiene-styrene (SBS) copolymer is the widely used one because of its better performance and compatibility with virgin asphalt. In this study, the existence of SBS modifier how to affect the interaction ability of filler particles to original asphalt was investigated via ∆G (i.e., complex modulus difference between asphalt matrix and corresponding mastic) and K-B-δ (i.e., asphalt-filler interaction evaluation indicator based on phase angle). The results showed that the addition of SBS modifier into Pen90 asphalt led to the increase in complex modulus and appearance of plateau region in phase angle. The ∆G and K-B-δ values of SBS asphalt mastics were larger than that of corresponding Pen90 asphalt mastics at low reduced frequency region (i.e., high temperature). These findings indicated the introduction of SBS copolymer can improvement the asphalt-filler interaction ability at certain conditions and the enhancement effect was stronger for the asphalt mastics prepared by fly ash by comparison in limestone. The influence mechanisms of SBS copolymer on asphalt-filler interaction were also discussed in this study. The formation of SBS rubber-elastic network and fast molecular motion at high temperatures attributed to the stronger asphalt-filler interaction degree. Additionally, abundant pores on the surface of fly ash particles provided opportunities to entangle with SBS and asphalt molecules and thus led to stronger interaction degree with Pen90 asphalt.</p>