The invention relates to an ultra-high density room-temperature sulfuration dual-component fireproof silicone rubber having good nuclear radiation shielding function used for places such as nuclear power station, hospital and nuclear submarine and a preparation method thereof, which belong to the field of a high-molecular sealing material. A fireproof silicone rubber is composed of a component A and a component B, according to weight part, the component A contains 100 parts of vinyl polysiloxane, 0.1-5 parts of a vinyl platinum catalyst, 0.5-30 parts of silica, 5-120 parts of an inorganic fire retardant, and 500-1000 parts of surface-modified metal powder; and the component B contains 100 parts of vinyl polysiloxane, 4-80 parts of polymethylhydrosiloxane, 0.5-30 parts of silica, 5-120 parts of an inorganic fire retardant, and 500-800 parts of the surface-modified metal powder. The prepared room-temperature sulfuration dual-component fireproof silicone rubber has higher tensile strength, the elongation at break and irradiation-resistant performance, a product with density exceeding 3.5 g/cm<3> is easily prepared, and the product life is longer.