The microstructure change of chlorinated rubber coating under artificial accelerated aging was charac terized by using impedance spectroscopy and infrared attenuated total reflection(ATR). The result indicats that after thermal oxidative aging in 130益,the chlorinated rubber coating released HCl gas and carbon鄄carbon double bond is formed. After hydrothermal aging in 85益,RH=75% besides the releasing of HCl gas and formation of carbon鄄carbon double bond, hydroxyl is found in the coating.