The invention belongs to the field of building decoration materials, and discloses a fireproof thermal insulation building material and a preparation method thereof. The material is prepared from sepiolite, Qi cotton, porous powder quartz, ceramic fiber, bentonite, a wetting agent, a binding agent, graphene, fire retardant, methyl silicone oil, methyl alkoxy silicone oil, amino silicon oil, polyethylene glycol, an emulsifier, fungicide, bagasse, rice hulls, rice bran, biomass insulation material additives, expanded perlite, vermiculite, quicklime, gypsum, straw stalk and rape stalk. The material has the thermal insulation and cold insulation effects, by using the building material, the thickness of the wall can be reduced, the thermal insulation and cold insulation effects are achieved, and the building material can be greatly saved. The paint is excellent in performance, good in freezing resistance and free of cracking and deformation; the fire retardant adopted by the building material adopts tetrabromobisphenol A, and the fire retardant is one of the fire retardant products which are most scientifically tested and have the highest cost advantage in the market.