Waste materials generated from the maintenance, rehabilitation, and reconstruction of asphalt pavements present challenges for resource recycling and environmental protection. This study investigates the multiscale rejuvenation mechanism of rejuvenated asphalt pavement binder modified with crude tall oil (CTO) and evaluates its sustainability. Molecular dynamics simulations combined with rheological tests were employed to examine the compatibility, viscosity, glass transition temperature, thermal properties, modulus, and viscoelasticity. Results show that the main components of CTO exhibit high compatibility with aged asphalt, particularly at elevated temperatures. Functional group analysis further supports this conclusion. Simulations reveal that tall oil reduces density, cohesive energy, and viscosity, enhances molecular mobility, and partially restores mechanical modulus. The master curve analysis demonstrates that CTO effectively facilitates the transition of reclaimed asphalt pavement (RAP) binder from elastic to viscous behavior at high temperatures, with the shear modulus restored by 64.3 %. Notably, the incorporation of tall oil slightly compromises thermal stability, increasing the risk of thermal expansion. Economic and environmental assessments further indicate that CTO is cost-effective and requires lower energy during the mixing process. This study advances understanding by linking molecular-level interactions to macroscopic performance, providing insights for the sustainable application of CTO in asphalt rejuvenation.