Abstract: Abstract: This article takes the "9·12" catastrophic explosion accident in Mile county as an example to analyze the direct causes of the accident and use the fault tree method to identify the root cause of the accident. Frank-Kamenetskii thermal spontaneous combustion theoretical model was used to study the explosion mechanism of ammonium nitrate. It was found that impurities would reduce the self-accelerating decomposition temperature of ammonium nitrate, and eventually lead to thermal explosion of ammonium nitrate. Finally, some suggestions on the storage and transportation of ammonium nitrate are given.

Key words: ammonium nitrate, the cause of the accident, Frank-Kamenetskii model, thermal explosion