The invention relates to a ternary electrolyte containing unsaturated carbon chains and preparation and application thereof, the electrolyte comprises boron trifluoride salt represented by a general formula I: in the general formula I, R, R1 or R4 are independently a first chain without or containing at least one atom; r, R1 and R4 are not none at the same time; any one atom of R, R1, R2, R3 or R4 is connected with-R5-OBF3M, and-R5-OBF3M is connected to any one atom of R, R1, R2, R3 or R4; r2, R3 or R5 are independently a second chain free of or containing at least one atom; m is a metal cation; the first chain and the second chain are carbon chains; h on any C in the first chain and the second chain can be independently substituted by a substituent group, and the first chain, the second chain and the chain substituent group at least contain one unsaturated bond. The boron trifluoride salt can be used as an additive in a battery and a polymeric monomer in a polymer electrolyte, can be applied to a liquid battery, a mixed solid-liquid battery, a semi-solid battery, a gel battery, a quasi-solid-state battery and an all-solid-state battery, and has a good effect.