The invention discloses a high-pressure electrolyte for a high-nickel ternary cathode material system lithium ion battery. The high-pressure electrolyte is composed of an organic solvent, an electrolyte lithium salt, a cathode film-forming additive, an anode film-forming additive and an anti-oxidation additive; the cathode film-forming additive is 1,5,2,4-dioxadithiane 2,2,4,4-tetraoxide, the anode film-forming additive is 4-fluoro-1,3-dioxolan-2-one, the anti-oxidation additive is tris[2-[2-(2-methoxyethoxy)ethoxy]ethyl]orthoborate, and by taking the total mass of the high-pressure electrolyte as a reference, the addition amount of the athode film-forming additive is 0.5-1%, the addition amount of the anode film-forming additive is 2-5%, and the addition amount of the anti-oxidation additive is 0.5-1%. The high-pressure electrolyte has relatively good oxidation resistance, high temperature resistance and safety characteristics, guarantees the battery to have relatively good cycle life, also has relatively high electrical conductivity, is capable of guaranteeing the high rate and power characteristics of the battery, also has relatively high safety, and is capable of substantially improving the safety performance of the power battery.