An improved one-pot method for the preparation of 2, 4, 5-trinitroimidazole from 4-nitroimidazole was reported.Its structure was identified by ¹H NMR, IR, MS and elemental analysis.The reaction time, reaction temperature and the molar ratio of the reagents of the synthetic route were optimized.Results show that the yield of 2, 4, 5-trinitroimidazole can reach up to 80.6% under the conditions of reaction time 4 h, reaction temperature 120 ℃ and the molar ratio of n (4-nitroimidazole):n(65% HNO₃):n(AcOH)=1:30:30.