To alleviate the shortage of petroleum asphalt and explore the feasibility of microalgae oil for asphalt modification and the long-term performance of modified asphalt, microalgae oil was obtained by degradation, centrifugation and extraction, and modified asphalt was prepared. The content of microalgae oil was determined by testing the ductility, softening point and viscosity of modified asphalt under different microalgae oil content. Through high and low temperature rheological test and mixture road performance test, the performance changes of microalgae oil modified asphalt after rolling thin film oven test (RTFOT) short-term aging, pressurized aging vessel (PAV) long-term aging and UV aging were analyzed and compared with SBS modified asphalt. The molecular structure and composition of microalgae oil modified asphalt were analyzed by infrared spectroscopy. The results show that when the content of microalgae oil is 30% (mass fraction of admixture), the ductility of modified asphalt reaches the maximum, and the softening point and viscosity meet the requirements of modified asphalt. After RTFOT short-term aging, the performance difference between microalgae oil modified asphalt and SBS modified asphalt is not significant. The resistances of PAV long-term aging and UV aging of microalgae oil modified asphalt are better than SBS modified asphalt, especially UV aging resistance. Infrared analysis shows that the two modified asphalts contain similar components such as a vinyl double bond, aromatic C-H, methyl and methylene, but the contents of aromatic C-H and telescopic C-C are different. Compared with SBS modified asphalt, microalgae oil modified asphalt increases amide unsaturated group and carboxyl group, which is conducive to the formation of network molecular structure of modified asphalt.