Excessive gamma rays will be emitted when a nuclear power plant is under overhaul, leading to a certain number of hotspots. To meet the shielding requirements of these hotspots, a new type of flexible shielding material with a “sandwich structure” has been developed. The new flexible shielding materials consist of two parts: one is silicone rubber with excellent physical and chemical properties by adding reasonable multicomponent additives as a matrix, and the other is lead powder as a shielding body. This kind of material, with lead powder dispersed uniformly in silicone rubber, was prepared through a mixing process. Based on this, the article has carried on the discussion with the performance of the functional layer of the new flexible shielding materials. The problem of the process stability of ultrafine powder distributed uniformly in a matrix with various densities among different regions has been solved as well. Furthermore, this kind of material has been adopted at the Chinese pressurized water reactor nuclear power plant as the first demonstration project. The site shielding effect has been recognized by the World Association of Nuclear Operators. As a result of this research, it is possible that the design of a radiation shield for a short or long time can be made quickly when a nuclear power plant is running or being overhauled. Meanwhile, this study is of great significance for the popularization and application of shielding materials.