The present invention relates to a thermosetting electrolyte composition for a lithium secondary battery, a gel polymer electrolyte prepared therefrom, and a lithium secondary battery including the gel polymer electrolyte, and particularly, to a thermosetting electrolyte composition for a lithium secondary battery, which includes LiPF6 as a first lithium salt, a second lithium salt excluding the LiPF6, a non-aqueous organic solvent, and a polymer or oligomer containing a unit represented by Formula 1, a gel polymer electrolyte prepared therefrom, and a lithium secondary battery including the gel polymer electrolyte.