In this paper, the NaAl(NH2)4 phase is successfully prepared from NaAlH4 reacting in liquid ammonia at low temperature, and the XRD pattern and FT-IR was used to the characterization. The decomposition process of the NaAl(NH2)4 were studied By thermoanalysis, XRD pattern and FT-IR, and product analysis of as-prepared samples at different temperature heat treatment. The experiments show that: The thermal decomposition of NaAl(NH2)4 under primary vacuum leads to the release of NH3 and completed at 250癈 with Two moles of NH3 released. Meanwhile, intermediate NaAl(NH)2 was amorphous and decomposed at about 113.8 ℃. In the complex NaAl(NH2)4, [NH2]? is covalently bonded with Al, and the same to N-H bone. In the pyrolysis process, [NH2]? - Al bone prior to break up, that lead to the formation of NH3. The final pyrolysis products of NaAl(NH2)4 is NaNH2, AlN and NH3.