The invention provides an improved inorganic noncombustible fireproof door and a processing method thereof. The fireproof door manufactured by the method has low processing cost, good fireproof property and fire resistance, and firm and reasonable structure. The fireproof door comprises a fireproof door frame and internal fireproof filler, and is characterized in that the door frame comprises a wooden framework; the surface of the wooden framework is stuck with a fireproof plate; and the fireproof filler is a whole block of fire-retardant core which is made of expanded perlite and fly ash. The processing method comprises the following steps: when the improved inorganic noncombustible fireproof door is manufactured, the fireproof plate is stuck on the surface of the framework, a layer of lubricating oil is coated on a stay plate, and the wooden framework is flatly placed on the stay plate; three portions of the expanded perlite, 1.5 portions of the fly ash and 1 portion of curing agentare mixed, and 0.5 portion of synthetic adhesive is added into mixed materials after the mixed materials are stirred for 1 minute, and then the mixed materials are uniformly stirred again; and the mixed materials which are uniformly mixed are filled into the wooden framework within 15 minutes to form a plate blank on which a high-temperature resistant flat plate is coated, the plate blank and thestay plate are sent into a chilling press for chill pressing together and are then sent into a hot press for hot pressing, and an upper cover plate is uncovered, so as to naturally cool the plate blank.