The 1-(p-dimethylaminophenyl)pentazole was synthesized at low temperature with sodium azide and p-dimethyldiazonium which was synthesized by coupling sodium nitrite with p-dimethylphenylenediamine dihydrochloride in aqueous media. Its structure was characterized by ¹H NMR at -20 ℃.The stability of 1-(p-dimethylaminophenyl)pentazole in solvent at different temperatures was further analyzed by ¹H NMR with a dynamic heating process from -50 ℃ to 25 ℃. It is concluded that the stability is less stable in solvent, and it decomposes almost at 25 ℃ for several minutes. According to the results of the ¹H NMR analysis, the reaction mechanism of decomposition and synthesis of arylpentazole, which was put forward by Bulter et al, are confirmed.