<p>Polymer-modified asphalt is currently a research focus in the field of pavement engineering. Crumb rubber (CR)/Styrene–Butadiene–Styrene (SBS) modified asphalt can reduce production costs while maintaining good performance, and CR activation has been demonstrated to be an effective approach for further improving modified asphalt properties. In this study, five types of CR with different activation degrees were used to prepare pretreated CR/SBS modified asphalts. Three aging conditions, short-term aging, long-term aging, and UV aging, were applied. The chemical composition, fatigue performance, and creep recovery behavior of the pretreated CR/SBS modified asphalts were investigated. The results show that with increasing activation degree, the bonding between CR particles is enhanced, leading to a more stable colloidal structure in the modified asphalt. Correspondingly, the asphaltene index decreases, with the maximum reduction reaching approximately 30% as the activation degree increases. Higher CR activation degrees enhance the internal cross-linked network structure, thereby reducing strain sensitivity and improving fatigue resistance under elevated strain levels. In addition, the stress sensitivity of the CR/SBS modified asphalt does not decrease linearly with increasing CR activation degree; once the activation degree exceeds a certain threshold, the stress sensitivity no longer decreases.</p>