The processes of supercritical water oxidation (SCWO) and wet air oxidation (WAO) are promising alternatives to incineration of aqueous recalcitrant organic waste streams, and had been compared with decomposition of aqueous solutions of ethylene glycols (HO(CH₂CH₂O)_nH). The SCWO experiments were performed in an isothermal tubular flow reactor at temperatures ranging from 380 to 425 ℃. The initial amount of air ranged from 100 to 400 % of stoichiometrically required amount of air for complete oxidation, while the operating pressure was maintained at 250 bar for all runs. The WAO experiments were studied in a batch autoclave reactor at temperature between 200 and 300 ℃ and stoichiometrically required oxygen ratio from 100 to 400 %. Though reaction times in WAO were up to several hours, a complete destruction of ethylene glycols (EGs) in SCWO required less than 1 min of reaction time under each conventional reaction condition. SCWO conditions increased the decomposition rate EG compounds (EG, DEG and TEG), EG was the most refractory compound, which has decomposed well at around 300 ℃ for WAO and 425 ℃ for SCWO. Whereas the increasing amount of oxygen required accelerated EG decomposition in WAO, it had little effect on EG destruction in SCWO. It suggests that the mass transfer limitation does not exist because oxygen became completely miscible with supercritical water, like single phase reaction under SCWO. Though SCWO process required more severe reaction conditions, SCWO dramatically increased the removal capacity and efficiency compare to WAO.