TThe Mullins effect refers to stress softening in rubber-like materials during loading after prior deformation. Although this phenomenon has been extensively studied, its strain-history dependence and recovery behavior in high-damping rubber (HDR) remain insufficiently quantified for engineering applications. This study experimentally investigates the Mullins effect of HDR under cyclic shear loading with variable and constant strain amplitudes. A cyclic shear test with variable amplitudes was used to evaluate the effects of maximum experienced strain and prior loading history, whereas repeated cyclic shear tests with a constant amplitude were performed after 1 day, 1 week, and 3 weeks to examine time-dependent recovery. The results show clear stress softening at all investigated strain levels, with the stress reduction decreasing from 37.62% at a strain level of 0.5 to 17.84% at a strain level of 2.5. The stress amplitude recovered rapidly, reaching 88.90%, 94.81%, and 97.43% after 1 day, 1 week, and 3 weeks, respectively. Based on the relationship between the stress ratio and accumulated absorbed energy, a phenomenological model is proposed to reproduce the Mullins effect in HDR