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• CQDs/SBS were prepared based on pickering emulsion polymerization. • The physical and chemical properties of CQDs/SBS were characterized. • The modification effect of CQDs/SBS on asphalt was studied. • The cost of CQDs/SBS and SBS modifiers was compared. • CQDs/SBS is a good modifier for asphalt with high performance and low cost. This research aims to use the prepared bio-base carbon quantum dots/styrene–butadiene styrene block copolymer (CQDs/SBS) composite materials as asphalt modifiers based on Pickering emulsion polymerization. The physical and chemical properties of CQDs/SBS composite modifier and its effect on asphalt modification were researched and contrasted it with SBS modifier. The results show that strong van der Waals forces and chemical covalent bonds are formed between CQDs and SBS polymer chains through a series of physicochemical reactions, resulting in strong interactions. Thus CQDs are uniformly dispersed in the SBS phase to form a homogeneous composite material. With the addition of CQDs, the CQDs/SBS composite modifier with slightly lower molecular weight than SBS modifier and can be better dispersed in asphalt. In addition, CQDs/SBS composite modifier has better thermal stability. Furthermore, CQDs and SBS have a synergistic impact in progressing the high-temperature property of polymer modified asphalt (PMA), which is showed by the improvement in softening point, viscosity, rutting resistance, and elastic recovery rate of CQDs/SBS PMA. However, the low-temperature property of CQDs/SBS PMA decreased, which is manifested by decreased penetration and ductility, increased creep stiffness modulus (S), and decreased the rate of change of stiffness with time (m). Further, CQDs/SBS PMA appears superior better storage stability than SBS PMA. It has the preferences of facile preparation procedure and low cost too, making it a beneficial choice for asphalt modifiers. [ABSTRACT FROM AUTHOR]