Alkanolamines such as MEA, DEA, MDEA and DIPA in aqueous solutions is frequently used for scrubbing carbon dioxide from natural gas. High quantity of alkanolamine appears in the wastewater during cleaning and maintenance as well as shutdown of the absorption and desorption columns. The alkanolamines waste is toxic to the environment and this wastewater cannot be treated in the conventional wastewater treatment. Advanced Oxidation Process (AOP) named UV/H2O2 is introduced to solve this problem. A laboratory set up of degradation MDEA waste using UV/H2O2 was conducted and the degradation mechanism has been studied. Glycine, oxalic acid, acetic acid, nitrate ion, nitrite ion and ammonium ion are identified as degradation intermediate product.