The invention relates to electrolyte, belonging to the technical field of material chemistry and high energy batteries. The electrolyte consists of an organic solvent, an additive and lithium salt, wherein the organic solvent is one or a mixture of ethylene carbonate, ethyl methyl carbonate, methyl-carbonate or diethyl carbonate; the additive is sulfurous ester; and the lithium salt is selected from lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, perfluoroalkyl lithium sulfonate, perfluoroalkyl sulfoacid imide lithium, annular perfluoroalkyl di(sulfonyl)lithium imide, perfluoroalkyl acyl sulfonate lithium methide, organic boric acid ester lithium, organic lithium phosphate or organic aluminic acid ester lithium. Due to the adoption of the electrolyte, a layer of stable solid electrolyte phase boundary face film can be formed on the surface of a graphite electrode, the compatibility between the electrolyte and an electrode material is improved, the temperature suitability of the electrolyte material is expanded through proportion optimization, and the cycle performance, rate capability and temperature suitability of a lithium secondary battery using the electrolyte can be effectively improved.