Abstract: The adiabatic decompositions of ammonium nitrate (AN) and non-explosive, irrestorable fertilizer-grade ammonium nitrate (NEIFAN) were investigated by accelerating rate calorimeter (ARC). The experimental data was processed with a dynamic model by means of a computer-control system. The curves of thermal decomposition temperature and pressure versus time, self-heating rate and pressure versus temperature, pseudo zero-order rate constant versus temperature and time to maximum rate versus temperature were obtained. The kinetic parameters such as apparent activation energy, pre-exponential factor, temperature of no return and self-accelerating decomposition temperature were calculated. All of the experimental results indicates that NEIFAN has better thermal stability and safety, and the diminishment or elimination of NEIFAN explosive characteristic is due to the improvement on its thermal stability.