The invention relates to a method for processing a metastable beta-type titanium alloy plate and belongs to the technical field of titanium alloy processing. The invention aims to overcome defects in the prior art, provides technology for processing a Ti-15-3 alloy plate and improves the cold working performance of alloy. The method for processing the metastable beta-type titanium alloy plate comprises the following steps of: smelting the titanium alloy plate into an ingot, charging at the temperature of between 800 and 850 DEG C and keeping the temperature for 100 to 150 minutes, raising the temperature to between 1,100 and 1,150 DEG C and keeping the temperature for 240 to 360 minutes, and finishing the first fire by repeatedly upsetting and drawing; drawing unidirectionally until cogging is finished so as to obtain a blank; sawing and rolling the plate blank into a hot-rolled plate blank with the thickness of 4 to 10 mm at the temperature of between 850 and 1,000 DEG C; and cold rolling to obtain a plate with the thickness of 1 to 3 mm after annealing and alkaline and acid washing. By controlling the rolling temperature, the deformation degree and the cooling speed after deformation, the method controls the structure of a forging stock to fully break the forging stock, and effectively suppresses phase precipitation resulting in a brittle alloy. Therefore, the cold working plasticity and cold working performance are improved.