The phase behavior of ionic liquids aqueous two-phase(ILATPS) was investigated.It was found that the additive salt had little effect on the phase equilibrium of aqueous two-phase. The effect of anion mainly obeyed the Hofmeister rule
and the formation of ILATPS could be promoted by the increase of the hydrophobicity of anion.The formation of ILATPS could also be promoted by the increase of polarity of the head group
and by the increase of the side-chain length of ionic liquids
but the effect was weaker than that anion.An elevated temperature would inhibit the formation of ILATPS for short-chain ionic liquids
but would promote the formation of ILATPS for long-chain ionic liquids.