AbstractTo optimize the rheological properties of warm-mix asphalt and analyze its ultraviolet (UV) aging behaviors, organic montmorillonite was selected to modify the Sasobit warm-mix asphalt. 3% Sasobit was added into the hot mix asphalt to prepare warm-mix asphalt; and then, three different contents of organic montmorillonite (1%, 2%, and 3%) were added to modify the warm-mix asphalt compositely. Subsequently, the road performance and UV aging behaviors of prepared asphalt were evaluated by some rheological indicators; and then, the modification mechanism was investigated by micro testing methods, including Fourier transform infrared spectroscopy (FTIR) test and Fluorescent microscope (FM) test. Results show that with the introduction of Sasobit, construction workability and high-temperature properties of hot mix asphalt were improved, while its fatigue performance and low-temperature properties were decreased. Fortunately, adding organic montmorillonite into the prepared warm-mix asphalt can significantly optimize its fatigue performance while having little influence on its low-temperature properties. UV aging test results show that DSRFn is the most sensitive indicator to characterize the UV aging behaviors of asphalt. Meanwhile, DSRFn aging indexes of warm-mix asphalt and those with 1%–3% organic montmorillonite were reduced by 28.88%, 46.41%, 48.55%, and 46.15%, respectively, compared with that of hot mix asphalt, indicating that Sasobit warm-mix asphalt has superior aging resistance than hot mix asphalt and that the addition of organic montmorillonite can further improve this ability. Microscope test results confirm that the intercalated structure or exfoliated structure may be formed in the asphalt binders, thereby enhancing the rheological properties. In accordance with the presented results, it is recommended that the optimum content of montmorillonite is 2%, which can promote the prepared asphalt samples to obtain excellent rheological properties.