Ionic liquids were proposed as the potential replacement to the traditional organic solvents and widely used in the formation of aqueous biphasic systems,due to their unique properties,including non-volatility,low toxicity,non flammability,high chemical and thermal stability.The aqueous biphasic systems based on ionic liquids offered their extensive benefits on the extraction of biomolecules and organic compounds,such as fast extraction,simple operation,easy scale and high biocompatibility without using the harmful organic solvents and complicated apparatus.In the paper,the phase separation mechanisms of aqueous biphasic systems and their applications in separation and purification of small organic molecules and biological samples were reviewed.The advantages,drawbacks and future development of the aqueous biphasic systems were also presented.