A method for making a solid electrolyte includes the following steps. A first monomer, a second monomer, an initiator and a lithium salt are provided. Wherein the first monomer is R1—OCH2—CH2—OnR2, the second monomer is R3—OCH2—CH2—OmR4, each “R1”, “R2” and “R3” includes —C═C— group or —C≡C— group, “R4” is an alkyl group or a hydrogen (H), and “m” and “n” represents an integer number, molecular weights of the first and second monomers are greater than or equal to 100, and less than or equal to 800. The first and second monomers, the initiator and the lithium salt are mixed to form a mixture, and a weight ratio of the first monomer to the second monomer is less than or equal to 50%. The first and second monomers are polymerized to form an interpenetrating polymer network, and the lithium salt is transformed into a solid solution and dispersing in the interpenetrating polymer network.