The invention relates to the technical field of a high-molecular material, and more specifically relates to a LCP/PBT/PET ternary alloy material and a preparation method thereof. The LCP/PBT/PET ternary alloy material comprises the following raw materials in parts by weight: 10-40 parts of a liquid crystal polymer, 10-40 parts of polybutylene telephthalate, 10-40 parts of polyethylene glycol terephthalate, 5-40 parts of glass fiber, 3-15 parts of a compatilizer, 3-15 parts of a fire retardant, 0.1-0.5 parts of an anti-oxidant, 0.2-2 parts of a lubricant and 1-2 parts of a modifier. The ternary alloy material has the excellent mechanical properties of toughness, impact strength, tensile strength and bending strength, and has the advantages of good fireproof performance, good heat resistance, low water absorption, good size stability, high crystallization efficiency, good moulding performance, good processing performance, low cost, and high usage value.