The invention discloses a sample plate for preparing a brittle hard metal microsphere coating and a processing method of the sample plate, and relates to the technical field of microsphere coating preparation. The sample plate solves the problem that a coating on the inner surface of an existing sample plate falls off, and disintegrating slag is generated and is attached to the surface of a microsphere, so that the surface roughness of the brittle hard metal coating on the surface of the microsphere is increased. According to the technical scheme, the inner surface of the sample plate is curved and rough, the outer side of the inner surface is sequentially coated with an aluminum coating and a graphite carbon coating, the aluminum coating can promote relaxation and release of stress of the brittle hard metal coating, and the graphite carbon coating can enhance the adhesive force between the brittle hard metal and the aluminum coating; and through the combined action of the two transition coatings, the brittle hard metal coating is prevented from falling off from the inner surface of the quartz sample plate and cracking, and the surface quality of the microsphere is improved. According to the processing method of the sample plate, an ion beam is adopted for carrying out surface etching and cleaning on the surface in the sample plate, and then the aluminum coating and the graphite carbon coating are sputtered separately. In addition, the sample plate can be repeatedly used after being simply processed.