The present invention discloses a preparing method of a Ti Al-based alloy plate, which relates to a preparing method of an alloy plate. The present invention solves the problems that the existing Ti Al-based alloy is not easy to process into to form at room temperature; Ti Al-based alloy plates prepared by powder metallurgy technique are easy to pollute by interstitial elements with many impurities containing oxygen; and Ti Al-based alloy plates prepared by casting metallurgy technique and precision casting art have the disadvantages of crude grain structure, low strength and loose structure.In the method, pure titanium grains are piled in a steel module to obtain a multi-hole titanium prefabricated body; an Al-Si alloy casting wire is cut into block bodies; the block bodies are arrangedon the multi-hole titanium prefabricated body to be sintered to obtain a Ti - Al double alloy complex body; the Ti - Al double alloy complex body is coldrolled to obtain a Ti - Al double alloy complex plate; the Ti - Al double alloy complex plate is sintered again, and is cooled to room temperature; the Ti - Al double alloy complex plate is retreated from the steel module to obtain the Ti Al-based alloy plate. The Ti Al-based alloy is processed to be formed at the room temperature, so the Ti Al-based alloy plate has the advantages of compaction, even structure, thin grain structure and high strength, and the negative effect of oxidation and impurities is reduced.