The present disclosure provides a lithium-ion secondary battery and an electrolyte thereof. The electrolyte comprises a lithium salt; a non-aqueous solvent and an additive comprising a first additive and a second additive, the first additive comprises at least one of vinylene carbonate and vinyl ethylene carbonate, the second additive is 4-methylene-1,3-dioxolan-2-one and its derivatives with a structural formula 1 and/or 4,5-dimethylene-1,3-dioxolan-2-one and its derivatives with a structural formula 2; in the structural formula 1 and the structural formula 2, R1, R2, R3 and R4 each are hydrogen, halogen, C1˜C3 alkyl or halogenated alkyl; a weight percentage of the first additive in the electrolyte is 0.2%˜2.0%, a weight percentage of the second additive in the electrolyte is 0.3%˜4.0%. The lithium-ion secondary battery comprises the aforementioned electrolyte. The lithium-ion secondary battery has better cycle performance, better low temperature discharging performance, and higher first coulombic efficiency.