In order to enhance the long-term resistance to cracking of asphalt pavement， a self-healing polyurethane modified asphalt based on dynamic disulfide bonds was developed. Polyurethane chain extender containing disulfide bonds （CY-OA） was synthesized using cystamine dihydrochloride as raw material， and disulfide bond-crosslinked polyurethane elastomer （PU-SS） was synthesized through stepwise copolymerization. PU-SS was mixed with asphalt to obtain self-healing polyurethane modified asphalt （PSA）. The physical and chemical properties， microscopic morphologies， and self-healing properties of PU-SS and PSA were studied. The results show that the addition of PU-SS improves the low-temperature deformation resistance of asphalt. The dynamic disulfide bond self-healing mechanism of PU-SS promotes the inherent self-healing ability of asphalt， achieving synergistic repair.