Imidazole based energetic compounds are one of the important directions on high energy compounds, and 5-cyano-4-aminoimidazole is the key intermediate for the design and synthesis of novel tetrazoyl imidaz-ole high energy and high nitrogen content compounds. With 5-carboxamide-4-amino imidazole (AICON) as raw material, the target compound 5-cyano-4-aminoimidazole (AICN) was obtained by its dehydration reaction with phosphoryl trichloride (POCl3). Through optimization of reaction system, reaction tempera-ture, reaction time and molar ratio, the yield and HPLC purity of AICN could achieve higher than 65% and 99.5%, respectively. Besides, the target compound was characterized by NMR, IR and element anal-ysis, and its thermal properties were investigated by TG. Results showed that the optimum reaction condi-tions was as follows: taking POCl3 as dehydrant, n(AICON) : n(POCl3) was 1:10, and reaction heating mode was that the reaction temperature rised rapidly to 80-85 ℃, maintained for 30 minutes, then de-creased to 70-75 ℃, and maintained for 1-1.5 h; there were two mass loss stages of AICN existed in the range of 40-1000 ℃, the corresponding decomposition temperature regions were 40-400 ℃ and 400-1000 ℃, the corresponding mass losses were 19.8% and 60.7%, and the peak values of thermal de-composition temperatures was 256.5 ℃ and 698.4 ℃, respectively, which indicated that 5-cyano-4-aminoimidazole had good thermal stability.