【Abstract】 This study was about the cloud point of alkyl polyoxyethylene (AEO 9) and aqueous two phase systems formed by AEO 9 aqueous solution It was shown that the cloud point of AEO 9 aqueous solution was related to the composition and aqueous two phase systems would be formed when the temperature was above the cloud point Salt has an important influence on the properties of AEO 9 solution It could lower the system cloud point and reverse surfactant rich phase and surfactant leau phase of aqueous two phase system.Methylene blue could be extracted to some extent in the aqueous two phase system of AEO 9 If the system contained ionic surfactant, the distribution coefficient ( D ) of methylene blue would be changed Cationic surfactant could make D larger and anionic surfactant could make D smaller The mechanism behind extraction in ATPS was discussed更多还原