The invention discloses a preheating box for graphite boats. The preheating box comprises a cover plate, a preheating box body and a heating element. The preheating box body comprises a top plate, a rear side plate and a bottom plate, and the cover plate comprises a left side plate, a right side plate and a front side plate. The top plate, the rear side plate, the bottom plate, the left side plate, the right side plate and the front side plate enclose a cavity for placing the graphite boats, and the heating element is disposed in the cavity. A left side heightening beam, a right side heightening beam and a front side heightening beam are separately arranged on the left side, the right side and the front side of the bottom plate, and the left side plate, the right side plate and the front side plate are separately supported on the left side heightening beam, the right side heightening beam and the front side heightening beam. Graphite boat channels are reserved between the front side heightening beam and the left side heightening beam and between the front side heightening beam and the right side heightening beam. The left end surface of the top plate is coplanar with the inner sidesurface of the left side plate, and the right end surface of the top plate is coplanar with the inner side surface of the right side plate. A lifting drive for driving the cover plate to rise and fall along the rear side plate is arranged between the cover plate and the preheating box body. The preheating box for the graphite boats has the advantages of heating specifically for the graphite boatsand occupying small space.