The invention discloses a preparation method for TC2 titanium alloy large-sized plate blanks. The preparation method comprises the following steps of: 1, cutting off dead head and ingot bottom of the TC2 titanium alloy cast ingot and removing pores from the surface skin of the cast ingot; 2, cogging and forging the TC2 titanium alloy cast ingot for one heating time; 3, forging the cast ingot subjected to cogging and forging for one heating time to obtain a square billet; 4, performing chamfering drawing-out forging on the square billet for one heating time to obtain the plate blank; and 5, polishing all sides of the plate blank so as to eliminate the defects generated on the surface of the plate blank in the forging process and caused by temperature drop to obtain the TC2 titanium alloy large-sized plate blank. Repeated upsetting is combined with drawing-out forging; grains of titanium alloy are crushed completely by using a large-tonnage fast forging machine and a low-temperature large press-down method, and the obtained plate blank has fine and uniform tissue. The TC2 titanium alloy plate blank prepared by the method has high surface quality and uniform tissue; the product has few internal defects and high stability; and the qualification rate of the products is greatly increased.