Epoxy resin is a widely utilized replacement material for the mural support layers, and its aging degradation can significantly affect both the stability and aesthetics of murals. To further investigate the aging characteristics and mechanisms of epoxy resin, and to clarify the detrimental effects of its aging process on murals, this study employed E44 bisphenol A epoxy resin along with mural plaster materials as laboratory aging samples. Additionally, natural aging samples were selected from the murals of Fengguo Temple and the tomb of Shi Shewu. Comprehensive analyses, including mass and volume measurement, mechanical performance evaluation, scanning electron microscopy (SEM), and Fourier transform infrared spectrometry (FTIR), were conducted to examine changes in the physical properties and chemical structures of the samples during aging. The findings indicate that under conditions primarily influenced by temperature and humidity, epoxy resin exhibited increased yellowing, reduced gloss, and decreased density. Furthermore, characteristic peaks associated with functional groups such as epoxide groups, hydroxyl groups, ether bonds, and benzene rings within the polymer chain were observed to weaken significantly or disappear over time. These observable changes may serve as quantitative indicators for assessing epoxy resin aging.  In the initial stages of aging, moisture absorption led to swelling in the epoxy resin sample due to interactions with its substrate. This resulted in internal stress imbalances that generated micro-cracks. As aging progressed, these micro-cracks continued to proliferate—deepening and expanding under the influence of water molecule—ultimately resulting in extensive voids that markedly reduced both the mechanical strength and adhesion capacity of the material. Thermal exposure induced free-radical chain reactions within the epoxy resin, compromising their molecular structure and consequently affecting internal cohesion alongside weather resistance. Thus it can be concluded that epoxy resin predominantly contributed to a decline or failure in adhesive strength over time. Epoxy resin primarily contributes to the deterioration of murals by compromising adhesion and support strength, which may result in weakening or loss of bond strength. Additionally, it inflicts damage on the mural itself due to the stress exerted at the interface between the plaster layer and epoxy resin composite materials. Consequently, this process leads to issues such as cracking, detachment, deep loss, and eventual loss of the mural.