The interactions between lysozyme and hydroxy-functionalized ionic liquids including 1-(2,3-dihydroxypropyl)-3-methylimidazolium chloride([2,3-dhpmim]Cl),1-(2,3-dihydroxy-propyl)-3-methylimidazolium tetrafluoroborate([2,3-dhpmim]BF4)and 1-(2,3-dihydroxypropyl)-3-methylimidazolium hexafluorophosphate([2,3-dhpmim]PF6)were studied by UV-Vis absorption and fluorescence spectra.The results indicated that the fluorescence quenching of lysozyme by hydroxy-functionalized ionic liquids performed in static quenching mode.The synchronous fluorescence spectra showed that the microenvironment of tryptophan residues was changed.The binding constants and binding sites of ionic liquids to lysozyme increased by the order of [2,3-dhpmim]Cl