The invention discloses a method for preparing a fireproof high-temperature resistant plate. The method comprises the following steps: uniformly mixing melamine, formaldehyde and water, adjusting the pH value of the system to be 9-9.7 by using sodium hydroxide, performing heating stirring, adding microcrystalline cellulose and cocamidopropyl betaine, adjusting the pH value of the system to 5-5.4 by using hydrochloric acid, adding castor oil and polyethylene glycol, stirring, and cooling so as to obtain pretreated microcrystalline cellulose; uniformly mixing phenolic aldehyde epoxy resin, polyamide resin, microencapsulated red phosphorus and ammonium polyphosphate, adding water and tartaric acid, uniformly stirring, further adding the pretreated microcrystalline cellulose, calcium sulfate, fumed silica, talcum powder and magnesium hydrate, uniformly mixing and stirring, performing pressing molding in a mold, and cooling to the room temperature, thereby obtaining the fireproof high-temperature resistant plate. The fireproof high-temperature resistant plate is good in compatibility, excellent in fire and high temperature resistance, excellent in water resistance and free of moisture absorption phenomenon.