The energetic material，ammonium dinitramide (ADN) NH₄N(NO₂)₂, has been investigated with regard to its thermal decomposition behavior by the technology of GC/MS. Thermal decomposition of ADN is observed at 120 ℃.The main pathway is based on the formation of NH₄NO₃ and N₂O,and the thermal decomposition of NH₄NO₃ to N₂O and H₂O at higher temperatures. Side reactions form NO₂,NO,N₂ and O₂.