In order to solve the problem of high cost and pollution for treatment of a large quantity of nitric acid in the nitration of 3-nitro-1, 2, 4-triazol-5-one(NTO), the nitration agent(70% nitric acid), which was designed and prepared by the addition of an appropriate amount of industrial nitric acid into waste acids, was used to synthesize NTO from 1, 2, 4-triazol-5-one with an average yield of 82% and purity of 99.9%.The products were characterized by IR, ¹³C NMR, ¹H NMR, MS and elemental analysis etc.The effects of various factors such as temperature and reaction time etc.on the yield of the nitration reaction were studied.It was experimentally found that the conditions of nitration reaction were optimized as:molar ratio of TO/HNO₃ 1/6, nitration temperature 60-65 ℃, reaction time 1 h.the new nitration agent(70% nitric acid)can be reused for ten times and the amount for the addition of nitric acid reduces by 67.6%.