To investigate the mechanism of strength enhancement of emulsified asphalt cold-recycled mixture under activation，firstly，the evolution of its pavement performance under the influence of activation was studied. Subsequently，the morphological changes in the interfacial transition zone（ITZ） under activation were analyzed using scanning electron microscopy（SEM），energy dispersive spectroscopy（EDS），and atomic force microscopy（AFM）. The relationship between mixture strength and ITZ morphology was also explored. Results show that the addition of the activator significantly improves the high-temperature performance，low-temperature performance，and water stability of the emulsified asphalt cold-recycled mixtures. The splitting strength of the activated mixture at 15 ℃ increases by 16.3% to 30.8% compared to the non-activated mixture. The interfacial structure of the activated mixture is more compact，with the ITZ width decreasing over curing time. After 7 days of curing，the ITZ width is reduced by 77.8% under activation compared to the non-activated state. Under activation，the light components in the old asphalt binder are effectively replenished，and the styrence-butadiene-styrence（SBS）in the activator could diffuse into the old binder to modify it，thereby promoting the integration of new and old binder.