The invention discloses lithium ion battery gel electrolyte and a preparation method thereof. The lithium ion battery gel electrolyte is characterized by comprising gel factors, an electrolyte solvent, an electrolyte lithium salt and functional additives, wherein the gel factors comprise a gel monomer, a cross-linking agent and an initiator; the gel monomer is an acrylic acid isocyano ester compound; the chemical structure formula of the acrylic acid isocyano ester compound is as shown in the specification, and in the formula, R is CH3, C2H5 or H, and n is greater than or equal to 10 and lessthan or equal to 100. By adopting the lithium ion battery gel electrolyte, the purpose of reducing the amount of gel factors is achieved on the basis that advantages of gel electrolyte are ensured, the viscosity of the gel electrolyte is reduced, and the electric conductivity of ions in the gel electrolyte is improved, so that on the premise that the security and the mechanical properties of a gelbattery are ensured, the electrochemical properties of the gel battery are improved.