Abstract: The corrosion resistance and aging mechanism of unsaturated polyester putty were investigated using electrochemical impedance spectroscopy and accelerated hydrothermal aging test. The results show that the electrolyte solution penetrated into the putty/aluminum alloy interface and electrochemical corrosion occurred after immersing in 3.5 wt.% NaCl solution for 6 hours. The impedance of unsaturated polyester putty decreased significantly and the protection ability of unsaturated polyester putty decreased rapidly. In the process of hydrothermal aging, the surface of unsaturated polyester putty became smooth with the aging and degradation of resin. The aging and degradation of resin also caused localized holes on the surface of unsaturated polyester putty, and the gloss and color difference increased gradually. Unsaturated polyester putty had post-curing phenomenon at the initial stage of aging, and aging and degradation were more prone to occur at the position of aromatic ester.