The invention discloses a silver-based solder alloy, which comprises: Cu, 26-28%; Ga, 3.5-5.5%; at least two of the following elements: Ni, 0.001-0.5%; Co, 0.001- 0.5%; Fe, 0.001-0.5%; at least one of the following elements: Au, 0.001-0.5%; Pt, 0.001-0.5%; Pd, 0.001-0.5%; at least one of the following elements: In, 0.001-0.5% %; Sn, 0.001-0.5%; at least one of the following elements: La, Ce, Pr, Nd, Sm, Eu, Er, Yb, Y and Sc; the balance is Ag. The invention further provides a preparation method of silver-based solder alloy and a preparation method of foil strip and wire. The silver-based solder alloy of the present invention saves the nickel-plating process in welding vacuum electronic devices, preventing it from polluting the environment; at the same time, it solves the problems that the welding temperature of the Ag-28Cu-xNi alloy is high and the melting point is inconsistent; the solder The material alloy brazing process is good, has good wettability, the brazing rate of Kovar alloy, stainless steel, etc. is higher than 95%, and the shear strength of the brazed joint is σ b ≥285MPa.