The synthesis of 3-nitro-1,2,4-triazole-5-one and its lead salt have been scaled up to 100 g process. In addition, the technological conditions of NTO′s preparation were optimized,i.e. raising the reaction temperature in two stages and reducing the amount of nitrating agent. The dependence of reaction time and reaction temperature on NTO′s yield were determined. The improvement of preparation technology has led to a high yield(81.8%) and top quality of NTO.