The invention discloses a lightening fireproof filling material for producing metal door by expanded perlite and a process for preparation. The material comprises expanded perlite, magnesium oxide, magnesium sulfate, calcium hydroxide, aqueous adhesive and water proofing agent, the volume weight is between 200-300kg / m3, the proportionings of each component according to weight percentage respectively are that the expanded perlite takes 45-65, the magnesium oxide takes 15-25, the magnesium sulfate takes 5-15, the calcium hydroxide takes 0.5-4 and the aqueous adhesive takes 2-5. Employing the technical scheme, the product has the advantages of high mechanical strength, light weight, high grade of fire resistance, good effect of sound absorption and acoustic insulation, strong anti-weatherability, heat insulation, heat preservation and energy conservation, easy production and no poison, on hazard and no radiation and the like. The product can be widely used in metal door industry, architectural materials industry and the related industries.