The invention relates to a gel electrolyte membrane, a lithium ion battery, and preparation methods therefor. The preparation method for the gel electrolyte membrane comprises the steps of providing a battery electrode plate; preparing gel electrolyte precursors of different viscosities; and forming the gel electrolyte membranes on at least one surface of the electrode plate by the gel electrolyte precursors of different viscosities, testing the mechanical strengths of the gel electrolyte membranes prepared from the gel electrolyte precursors of different viscosities, making a corresponding viscosity-mechanical strength standard curve, and obtaining a target gel electrolyte membrane prepared by selecting the gel electrolyte precursors of different viscosities according to the standard curve corresponding to the predetermined mechanical strength of the target gel electrolyte membrane. The invention also relates to the gel electrolyte membrane prepared by the method, and also relates to a preparation method for the lithium ion battery which is prepared from a gel electrolyte membrane cell after the gel electrolyte membrane cell is obtained by adopting the gel electrolyte membrane, and the lithium ion battery prepared by the lithium ion battery preparation method.