The invention discloses high-temperature-resistant anti-radiation mortar and a preparation method thereof, and belongs to the technical field of anti-radiation mortar. The high-temperature-resistant anti-radiation mortar consists of the following components in parts by weight: 5 to 15 parts of cement, 6 to 10 parts of mineral powder, 3 to 5 parts of dispersed emulsion powder, 30 to 50 parts of vitrified micro-beads, 2 to 4 parts of glass fibres, 2 to 4 parts of aluminium oxide, 3 to 5 parts of perlite powder, 5 to 7 parts of nano-lead particles, and 2 to 4 parts of rubber powder. The invention aims to provide the high-temperature-resistant anti-radiation mortar and the preparation method thereof. The inherent characteristics of the aluminium oxide and the nano-lead particles are utilized and are combined with the interactions of other components, so that the high-temperature-resistant anti-radiation mortar has good rigid-flexible characteristics, does not layer, segregate and sag, has high structural stability under a high temperature, and meanwhile, has the characteristics of corrosion resistance, wear resistance and the like, and has high anti-radiation performance; the safety level of the anti-radiation mortar is improved.