Abstract: Morphological and structural changes of ethylene-propylene-diene monomer(EPDM) in indoor-accelerated aging test and atmospheric exposure test were investigated by gloss meter,scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FTIR).Correlation analysis was applied to discuss the outdoor and indoor apparent aging properties of EPDM.The results show that the gloss does not change in salt-fog test.In fluorescent UV test,the gloss decreases rapidly in the initial stage of aging and then reaches a plateau.The gloss changes inconspicuously in the initial stage of aging and then decreases with the aging time prolonging in atmospheric exposure test in the Xisha islands.The trend of gloss in indoor UV and salt-fog composite circulation experiment is similar to atmospheric exposure test in the Xisha islands.Atmospheric exposure test in the Xisha islands and indoor UV and salt-fog composite circulation experiment have a better correlation.Based on the analysis of gloss,the accelerated aging multiple of indoor UV and salt-fog composite circulation experiment is 25 to 26.FTIR spectra imply that β-diketone may form after EPDM is exposed to the artificial weathering environment produced by indoor UV and salt-fog composite circulation experiment and atmospheric exposure test in the Xisha islands.β-diketone is not formed in the salt-fog test condition.