The invention discloses a preparing method of a tungsten-copper alloy plate. The method is characterized by comprising the following steps of 1, carrying out air-stream smashing on tungsten-copper composite powder; 2, adding plasticizer into an internal mixer, and then slowly adding the tungsten-copper composite powder subjected to air-stream smashing, uniformly kneading the powder, and then breaking the powder to prepare plastic feeding particles; 3, after smashing the plastic feeding particles, adding the smashed plastic feeding particles into an extruder for being subjected to extrusion, and then calendaring the extruded plastic feeding particles to prepare a banding blank material; 4, carrying out thermal debinding on the banding blank material to prepare a degreased blank; 5, carrying out high temperature sintering on the degreased blank to prepare a sintered blank; 6, carrying out cold rolling on the sintered blank for shaping, and obtaining the tungsten-copper alloy plate after annealing. The density of the banding blank material of the plate prepared through the method provided by the invention is sufficient, so that the possibility of generating defects in the subsequent pressure processing is reduced, the defects, such as microcracks and fracturing are not easily generated, and the rate of finished products is high.