Ammonium 2, 4, 5-trinitroimidazole was synthesized by a new method, using 4-nitroimidazole as primary materials, followed by iodinaton, nitralysis and salifying with ammonia in yield of 33.3%. The structure was confirmed by MS and IR. Thermal behavior of ammonium 2, 4, 5-trinitroimidazole was studied by DSC and TG, melting and decomposition temperatures are 254.52 ℃ and 308.31 ℃, and the mass loss due to overall reaction (203.6-399.9 ℃) is 94%. Friction and impact sensitivities are 2% and 18%, respectively, and it was a low sensitivity energetic materials.