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In environmental conditions, the ultraviolet (UV) light from sunshine will trigger epoxy asphalt (EA) paving materials aging and performance reduction. This work studied the influence of UV aging on the structure and mechanical performance of cold‐mixed epoxy asphalt (CEA) to evaluate its aging mechanism. The chemical structure of CEA was tested by Fourier transform infrared spectra, X‐ray photoelectron spectroscopy, and micromorphology was observed through fluorescence microscopy. The mechanical properties of CEA were studied by tensile tests and dynamic mechanical analysis. The results indicated that the toughness of CEA went down due to UV aging, and the elongation at break and glass transition temperature decreased by 35.5% and 6.0°C, respectively. Based on structural analysis, the UV aging mechanism of CEA was summarized as follows: (1) the curing network of epoxy resin was partially broken, and the asphalt particle aggregated; (2) the asphalt and epoxy resin in UV aging‐CEA were oxidized and formed carbonyl group and sulfonic group. Highlights: Both asphalt and ER components in CEA underwent oxidation reactions and formed more CO, SO, and CO groups.UV‐CEA showed a decrease in toughness due to destruction of the cured ER cross‐linked network and shortening of the asphalt molecular chainE' and Tg of UV‐CEA was decreased, resulting from a decrease in ER crosslink density and an increase in molecular chain segment mobility of ER and asphalt. [ABSTRACT FROM AUTHOR]