The invention discloses a lithium sulfide solid electrolyte material with the addition of lithium-tin alloy and a silver halogen compound and a preparation method thereof. The preparation method comprises the following steps: (1) weighing lithium sulfide, phosphorus sulfide, lithium-tin alloy powder and sulfur according to the molar ratio of (2.5 to 4.0) to (0.5 to 1.0) to (0.02 to 0. 1) to (0.01 to 0.05) under an atmosphere protection condition, and uniformly mixing, thus obtaining a lithium-sulfur-phosphorus-tin mixture; (2) taking and putting the lithium-sulfur-phosphorus-tin mixture, silver iodide, silver bromide and silver chloride in a ball-milling tank under atmosphere protection and safe red light conditions, and carrying out ball milling, thus obtaining an amorphous lithium-sulfur-phosphorus-tin mixture containing the silver iodide, the silver bromide and the silver chloride; (3) sealing the amorphous lithium-sulfur-phosphorus-tin mixture obtained in the step (2) under the atmosphere protection condition, and heating to 60 to 180 DEG C under a vacuum condition for carrying out thermal treatment, thus obtaining the lithium sulfide solid electrolyte material. According to the preparation method disclosed by the invention, the lithium ionic conductivity of the obtained lithium sulfide solid electrolyte material is increased by simultaneously adding the lithium-tin alloy and the silver halogen compound.