In this work, temperature dependence of phase behaviors for the [Bmim]BF4 + sucrose + water system was investigated. It was found that interaction of [Bmim]BF4 with sucrose is exothermic, and lowering temperature is favorable for phase separation. In addition, a "[Bmim](+)-induced structural changes" model was developed and used to interpret the temperature effect, whereby the salting-out effect was thought to be an entropy driving process through analysis of the structural interaction and the electrostatic interaction.